N95 Respirators and Surgical Masks
With the advent of a novel H1N1 influenza outbreak in spring 2009 and the expectation of a second wave during the 2009–2010 flu season, there has been considerable interest in the use of surgical masks (facemasks) and respirators as infection control measures. Although their appearance is often similar, respirators are designed and engineered for distinctly different functions than surgical masks. The amount of exposure reduction offered by respirators and surgical masks differs. The National Institute for Occupational Safety and Health (NIOSH) and the Centers for Disease Control and Prevention (CDC) recommend the use of a NIOSH-certified N95 or better respirator for the protection of healthcare workers who come in direct contact with patients with H1N1.
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Evolution of Respiratory Protection against Particulate Exposures
Early surgical masks were constructed from layers of cotton gauze. They were first worn by surgery staff in the early 1900s to prevent contamination of open surgical wounds. With time their design, function, and use have expanded. Today surgical masks are worn in a wide range of healthcare settings to protect patients from the wearers' respiratory emissions. A surgical mask is a loose-fitting, disposable device that prevents the release of potential contaminants from the user into their immediate environment. In the U.S., surgical masks are cleared for marketing by the U.S. Food and Drug Administration (FDA). They may be labeled as surgical, laser, isolation, dental, or medical procedure masks. They may come with or without a face shield. Since OSHA issued the Bloodborne Pathogens Standard (29 CFR 1910.1030) in 1991, surgical masks have been recommended as part of universal precautions to protect the wearer from direct splashes and sprays of infectious blood or body fluids. (The FDA offers further information on surgical masks.)
The first modern respirators were also developed in the early 1900s. The impetus for their development derived from the need to protect miners from hazardous dusts and gases, soldiers from chemical warfare agents, and firefighters from smoke and carbon monoxide. In 1919, the U.S. Bureau of Mines published the first respirator performance standards for self-contained breathing apparatus for use in mines and for gas masks for use by soldiers against chemical warfare agents. Today respirators are found in a broad range of workplaces. Their use in healthcare settings dates to the 1990s in response to concerns about employee exposures to drug-resistant tuberculosis. Healthcare worker illnesses and deaths during outbreaks of severe acute respiratory syndrome (SARS) in the early 2000s led to renewed attention to the use of respirators for some infectious respiratory diseases. Most recently, planning efforts for pandemic influenza in 2006-07 led to considerable discussion about the role of small particle inhalation in disease transmission and the use of respirators to protect healthcare personnel from airborne influenza particles. A listing of all NIOSH-approved disposable, or filtering facepiece, respirators is available. NIOSH also maintains a database of all NIOSH-approved respirators regardless of respirator type—the Certified Equipment List.
Whether the goal is to prevent the outward escape of user-generated aerosols or the inward transport of hazardous airborne particles, there are two important aspects of performance. First, the filter must be able to capture the full range of hazardous particles, typically within a wide range of sizes (<1 to >100 µm) over a range of airflow (approximately 10 to 100 L/min). Second, leakage must be prevented at the boundary of the facepiece and the face. However, it is not possible to assure the latter—good face seal performance—without first ensuring a well-functioning filter.
Filter Performance
The filters used in modern surgical masks and respirators are considered "fibrous" in nature—constructed from flat, nonwoven mats of fine fibers. Fiber diameter, porosity (the ratio of open space to fibers) and filter thickness all play a role in how well a filter collects particles. In all fibrous filters, three "mechanical" collection mechanisms operate to capture particles: inertial impaction, interception, and diffusion. Inertial impaction and interception are the mechanisms responsible for collecting larger particles, while diffusion is the mechanism responsible for collecting smaller particles. In some fibrous filters constructed from charged fibers, an additional mechanism of electrostatic attraction also operates. This mechanism aids in the collection of both larger and smaller particle sizes. This latter mechanism is very important to filtering facepiece respirator filters that meet the stringent NIOSH filter efficiency and breathing resistance requirements because it enhances particle collection without increasing breathing resistance.
How do filters collect particles?
These capture, or filtration, mechanisms are described as follows:
- Inertial impaction: With this mechanism, particles having too much inertia due to size or mass cannot follow the airstream as it is diverted around a filter fiber. This mechanism is responsible for collecting larger particles.
- Interception: As particles pass close to a filter fiber, they may be intercepted by the fiber. Again, this mechanism is responsible for collecting larger particles.
- Diffusion: Small particles are constantly bombarded by air molecules, which causes them to deviate from the airstream and come into contact with a filter fiber. This mechanism is responsible for collecting smaller particles.
- Electrostatic attraction: Oppositely charged particles are attracted to a charged fiber. This collection mechanism does not favor a certain particle size.
In all cases, once a particle comes in contact with a filter fiber, it is removed from the airstream and strongly held by molecular attractive forces. It is very difficult for such particles to be removed once they are collected. As seen in Figure 2, there is a particle size at which none of the "mechanical" collection mechanisms (interception, impaction, or diffusion) is particularly effective. This "most penetrating particle size" (MPPS) marks the best point at which to measure filter performance. If the filter demonstrates a high level of performance at the MPPS, then particles both smaller AND larger will be collected with even higher performance.
This is perhaps the most misunderstood aspect of filter performance and bears repeating. Filters do NOT act as sieves. One of the best tests of a filter's performance involves measuring particle collection at its most penetrating particle size, which ensures better performance for larger and smaller particles. Further, the filter's collection efficiency is a function of the size of the particles, and is not dependent on whether they are bioaerosols or inert particles.
How are surgical masks and respirator filters tested?
Respirator filters must meet stringent certification tests (42 CFR Part 84) established by NIOSH. The NIOSH tests use what are considered "worst case" parameters, including:
- A sodium chloride (for N-series filters) or a dioctyl phthalate oil (for R- and P-series filters) test aerosol with a mass median aerodynamic diameter particle of about 0.3 µm, which is in the MPPS-range for most filters
- Airflow rate of 85 L/min, which represents a moderately-high work rate
- Conditioning at 85% relative humidity and 38°C for 24 hours prior to testing
- An initial breathing resistance (resistance to airflow) not exceeding 35 mm water column* height pressure and initial exhalation resistance not exceeding 25 mm water column height pressure
- A charge-neutralized aerosol
- Aerosol loading conducted to a minimum of 200 mg, which represents a very high workplace exposure
- The filter efficiency cannot fall below the certification class level at any time during the NIOSH certification tests
* Millimeters (mm) of water column is a unit for pressure measurement of small pressure differences. It is defined as the pressure exerted by a column of water of 1 millimeter in height at defined conditions, for example 39°F (4°C) at standard gravity.
As a result of these stringent performance parameters, fiber diameters, porosity, and filter thicknesses of all particulate filters used in NIOSH-certified respirators, including N95s, are designed and engineered to provide very high levels of particle collection efficiencies at their MPPS.
Manufacturers of surgical masks, on the other hand, must demonstrate that their product is at least as good as a mask already on the market to obtain "clearance" for marketing. Manufacturers may choose from filter tests using a biological organism aerosol at an airflow of 28 L/min (bacterial filtration efficiency) or an aerosol of 0.1 µm latex spheres and a velocity ranging from 0.5 to 25 cm/sec (particulate filtration efficiency). It is important to note that the Food and Drug Administration specifies that the latex sphere aerosol must not be charge-neutralized.
The generation of the test aerosol can impart a charge on a higher percentage of the aerosolized particles than may normally be expected in workplace exposures. A charge-neutralized test aerosol, like those used in the NIOSH tests, has the charges on the aerosolized particles reduced to an equilibrium condition. Therefore, higher filter efficiency values than would be expected with the use of charge-neutralized aerosols may result due to the collection of charged particles by the filters' electrostatic attraction properties. Additionally, allowing the manufacturer to select from a range of air velocity means that the test results can be easily manipulated. In general, particles are collected with higher efficiency at lower velocity through a filter.
Both of these aspects yield a test that is not necessarily "worst case" for a surgical mask filter. Because the performance parameters for surgical masks are less stringent than those required for filters used in NIOSH-certified respirators, the fiber diameters, porosity, and filter thicknesses found in surgical masks are designed with significantly lower levels of particle collection efficiencies at their MPPS.
How do surgical mask and respirator filters perform?
Respirator filters that collect at least 95% of the challenge aerosol are given a 95 rating. Those that collect at least 99% receive a "99" rating. And those that collect at least 99.97% (essentially 100%) receive a "100" rating. Respirator filters are rated as N, R, or P for their level of protection against oil aerosols. This rating is important in industry because some industrial oils can remove electrostatic charges from the filter media, thereby degrading (reducing) the filter efficiency performance. Respirators are rated "N" if they are not resistant to oil, "R" if somewhat resistant to oil, and "P" if strongly resistant (oil proof). Thus, there are nine types of particulate respirator filters:
- N95, N-99, and N-100
- R-95, R-99, and R-100
- P-95, P-99, and P-100
Respirator filters are tested by NIOSH at the time of application and periodically afterward to ensure that they continue to meet the certification test criteria. The FDA does not perform an independent evaluation of surgical mask filter performance, nor does it publish manufacturers' test results. In many cases it is difficult to find information about the filter test results for FDA-cleared surgical masks. The class of FDA-cleared surgical masks known as Surgical N95 Respirators is the one clear exception to this uncertainty of filter performance. This is the only type of surgical mask that includes evaluation to the stringent NIOSH standards. All members of this class of surgical masks have been approved by NIOSH as N95 respirators prior to their clearance by the FDA as surgical masks. The FDA, in part, accepts the NIOSH filter efficiency and breathing resistance test results as exceeding the usual surgical mask requirements.
In studies comparing the performance of surgical mask filters using a standardized airflow, filter performance has been shown to be highly variable. Collection efficiency of surgical mask filters can range from less than 10% to nearly 90% for different manufacturers' masks when measured using the test parameters for NIOSH certification. Published results on the FDA-required tests (if available) are not predictive of their performance in these studies.
It is important to keep in mind that overall performance of any facepiece for particulate filtering depends, first, on good filter performance. A facepiece or mask that fits well to the face but has a poor filter will not be able to provide a high level of protection.
Respirator and Surgical Mask Fit
Because respirator filters must meet stringent certification requirements, they will always demonstrate a very high level of collection efficiency for the broad range of aerosols encountered in workplaces. There has been some recent concern that respirator filters will not collect nano-sized particles, but research has demonstrated that such particles are collected with efficiencies that meet NIOSH standards. This is not surprising, because NIOSH tests employ small, charge-neutralized, relatively monodisperse aerosol particles and a high airflow.
Thus, the most important aspect of a NIOSH-certified respirator's performance will be how well it fits to the face and minimizes the degree of leakage around the facepiece. This must be measured for each individual and their selected respirator. Selecting the right respirator for a particular workplace exposure depends largely on selecting the right level of protection.
Respirator fit depends on two important design characteristics:
- Whether the respirator operates in a "negative pressure" or "positive pressure" mode
- The type of facepiece and degree of coverage on the face
Respirators that operate in a "negative pressure" mode require the wearer to draw air through an air-cleaning device (filter or chemical cartridge) into the facepiece, which creates a pressure inside the respirator that is negative in comparison to that outside the facepiece. A "positive pressure" respirator, on the other hand, pushes clean air into the facepiece through the use of a fan or compressor, creating a positive pressure inside the facepiece when compared to the outside. Negative pressure respirators inherently offer less protection than positive pressure respirators, because inward leakage occurs more easily in the former.
The facepiece design is also very important—some designs fit on the face better than others. It is more difficult to fit a half-facepiece respirator (one that covers the mouth and nose only) than a full-facepiece respirator (one that also covers the eyes). The nose and chin are the most difficult facial features on which to establish a tight fit. The fit of a hood, helmet or "loose-fitting" facepiece is highly dependent on the specific design and configuration. More details on the different classes of respirators and their levels of protection, can be found on the NIOSH respirator topic page and the OSHA Respiratory Protection Standard
Because fit is so important, NIOSH recommends and OSHA requires that each respirator wearer receive an initial fit test and annual fit tests thereafter. It is not possible to predict how well a respirator will fit on a particular face, even for respirators that fit well on a broad range of facial sizes. The FDA does not recommend or require any test of fit for surgical masks. A very limited number of published studies are available on this aspect of surgical mask performance. Three clinical studies conducted in the 1980s and 90s found no difference in surgical infection rates when staff did not wear surgical masks.1, 2, 3
A recent laboratory study of five surgical masks with "good" filters found that 80–100% of subjects failed an OSHA-accepted qualitative fit test using Bitrex (a bitter tasting aerosol) and quantitative fit factors ranged from 4–8 (12–25% leakage) using a TSI Portacount.4 In contrast, the least protective type of respirator (negative pressure half mask) must have a fit factor (outside particle concentration divided by inside concentration) of at least 100 (1% leakage).
NIOSH would like to hear from you regarding your experiences working with NIOSH-approved respirators and FDA-cleared surgical masks. For example, are there user needs for increased comfort and wearability that NIOSH could help address? Do users feel that exhalation valves on disposable, filtering facepiece impact the wearer's ability to successfully perform a user seal check? Are there certain aspects of filtering facepiece respirator design that could be improved for better fit? How would you compare the comfort and wearability of surgical masks and filtering facepiece respirators?
Additionally, the NIOSH Respirator Trusted-Source Information Page can help users identify NIOSH-approved respirators and learn how to use and obtain these products.
—Lisa Brosseau, Sc.D., and Roland Berry Ann
Dr. Brosseau is a faculty member in the University of Minnesota's School of Public Health whose research focuses on the performance of respiratory protection, measurement of aerosols, and assessment of workplace exposures to hazardous materials and wastes. Dr. Brosseau was Chair of the ACGIH Threshold Limit Values for Chemical Substances Committee from 1995–2005 and is currently Vice Chair Elect of ACGIH.
Mr. Berry Ann is the Deputy Director of the NIOSH National Personal Protective Technology Laboratory. He has more than 15 years experience working in respirator certification and PPT issues at NIOSH.
References
- Orr, N. W. 1981. Is a mask necessary in the operating theatre? Annals of the Royal College of Surgeons of England 63, (6) (Nov): 390-2.
- Mitchell, N. J., and S. Hunt. 1991. Surgical face masks in modern operating rooms—a costly and unnecessary ritual? The Journal of Hospital Infection 18, (3) (Jul): 239-42.
- Tunevall, T. G. 1991. Postoperative wound infections and surgical face masks: A controlled study. World Journal of Surgery 15, (3) (May-Jun): 383,7; discussion 387-8.
- Oberg, T., and L. M. Brosseau. 2008. Surgical mask filter and fit performance. American Journal of Infection Control 36, (4) (May): 276-82.
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Comments
Influenza virus is spread through viral contact with mucous membranes.
This is even stated in the CDC interim guidelines. It is not spread from inhaling respiratory particles as with tuberculosis. You can campare surgical masks to N95 respirators all you want. You are not researching the real issue, protecting the exposed mucous memebranes. The appropriate mask for any influenza or other virus spread via droplet would be a fluid shield or a mask and goggles. It seems to me that the obvious is being over looked.
Posted 10/15/09 at 11:41 am
Presentations made at the IOM meeting in August indicate that influenza transmission is also associated with close range exposure to small particles generated during speaking, coughing, and sneezing (links are included below). The traditional infection control paradigm does not consider this type of exposure. Surgical masks do not provide wearer protection for exposures to small particles (due to poor filtration and fit performance). Respirators are designed to offer such protection.
The following isolation precautions are recommended for healthcare personnel who are in close contact with patients with suspected or confirmed 2009 H1N1 influenza. For the purposes of this document, close contact is defined as working within 6 feet of the patient or entering into a small enclosed airspace shared with the patient (e.g., average patient room):
Standard Precautions - For all patient care, use nonsterile gloves for any contact with potentially infectious material, followed by hand hygiene immediately after glove removal; use gowns along with eye protection for any activity that might generate splashes of respiratory secretions or other infectious material.
Posted 10/19/09 at 10:50 am
Having functioned in hospitals as an Infection Control Nurse, I became interested in the use of masks in the late '60s. I was told by a surgeon that his mask became so saturated with his "respiratory leftovers", that he was sure he was spewing possibly his possibly infectious body waste into open patient cavities. PObviously that was incentive for me to monitor post-op infection rates closely.
It was easier to do then, as patients remained in hospital longer and Staff Nurse observations were communicated to Infection Control Nurses. Now, however, with earlier discharges following "micro-surgeries", follow up is a sometime thing. HH workers and family members who change post op dressings don't wear masks to do that. However, the infection rates have more to do with the length of time it takes wounds to heal, rather than the organisms present in the staff giving care.
The exception is Long Term Care Facilities, which further illustrates that. Colonization of microorganisms is found frequently in catheterized patients and thiose with open skin lesions; and when all patients are treated in a timely manner, that resolves. The source has most often been in staff members using medical equipment jointly. That has resulted in individual purchase by nurses' of their own stethascopes, and more diligent use of disinfectants when another staff member uses theirs.
It is heartening to see the advances in the manufacture of surgical masks/respirators. I'd like to know how much study is happening to compare post-op infection rates with their use, and the earlier ones, without their use.
Posted 10/15/09 at 12:02 pm
From a nursing education standpoint, is there any guidelines for fit testing of students for clinical experiences for the N95 masks? Thank you for the feedback-
Posted 10/15/09 at 12:47 pm
The guidelines for fit testing are the same for all respirator users. The American National Standard for Respirator Fit Testing Methods (ANSI Z88.10-2001) is a national consensus standard that provides guidance on how to conduct fit testing of tight fitting respirators (like N95 respirators), and the appropriate methods to use. Additionally, Paragraph (f)(1) of the Occupational Safety and Health Administration (OSHA) Respiratory Protection Standard (29 CFR 1910.134) requires that all tight-fitting respirators be fit tested in accordance with the requirements of the standard, including the fit test methods described in Appendix AMandatory Fit Test Protocols. Either of these references should provide you with the guidelines for fit testing of the students you are seeking.
Posted 10/16/09 at 2:51 pm
I am an Infection Preventionist. We know that H1N1 is spread by large droplets as is other influenzas. If it is recommended that HCWs wear N95 respirators to deal with confirmed or suspected H1N1 then I would want to know why this not considered an Airborne disease requiring a neg. pressure room. N95 masks are difficult to come by and require fit testing and education for them to be effective. It is a burden on the hospital to provide this level of protection for a disease that is considered to spread by large droplets and contact with the secretions. I like many other Infection Preventionists do not understand the recommendation for N95 respiratory protection for anything other than those procedures that cause aerosolization of the virus.....seems like over kill.
Posted 10/15/09 at 12:48 pm
The current evidence in support of airborne transmission of influenza has been discussed in a recent Institute of Medicine report, Respiratory Protection for Healthcare Workers in the Workplace Against Novel H1N1 Influenza A: A Letter Report.
Although there is strong evidence to support airborne transmission across short distances as a potential mode of transmission, there is not evidence to suggest that this agent is able to transmit over long distances (such as through air handling systems) or to cause prolonged airspace contamination. Thus, it differs from agents such as TB. In view of this, CDC guidelines recommend respiratory protection for close contact, defined as a distance of fewer than 6 feet from a patient or entry into a shared airspace equivalent to a typical patient room. Use of negative pressure, airborne infection isolation rooms is only recommended for aerosol-generating procedures (as feasible, since CPR and intubation are noted to be aerosol-generating procedures). The guidelines also recognize the supply issues that many facilities have faced in obtaining disposable N95 respirators and offer a range of practical options for dealing with those shortages.
[David Weissman is Director of the NIOSH Division of Respiratory Disease Studies]Posted 10/19/09 at 2:26 pm
How do the mask work with Beryllium? When it is very hot in the plant, the mask slip on the face from the sweat! when you take the mask off there is a black mark on your face that matches the outline of the mask. How well is the employee protected in this case?
Posted 10/15/09 at 1:00 pm
The current NIOSH respirator recommendations for Beryllium exposures, as stated in the NIOSH Pocket Guide to Chemical Hazards, are limited to:
(APF = 10,000) Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode
(APF = 10,000) Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained positive-pressure breathing apparatus.
Your employer's respiratory protection program has apparently determined that the protection level offered by the half-mask, filtering facepiece respirator is appropriate for your workplace exposures. However, your report of respirator slippage on your face during normal work activities should be brought to the attention of your Respiratory Program Administrator. The use of the current respirator should be re-evaluated, since the protection being provided is likely to be adversely affected with changes to the facepiece-to-face fit as the respirator slips. This assessment needs to be done in the workplace to determine the type and level of respiratory protection required for the exposures and work activities normally encountered. You should contact your Respiratory Program manager to discuss the situation and determine other types of respirators that may be available for your use.
Posted 11/9/09 at 11:36 pm
Nurses and other caregivers in our intensive care units found themselves working for extremely long periods of time, caring for very ill patients with confirmed or suspected nH1N1 cases during the late Spring-early Summer period just passed. Not surprisingly, they found the N95's became soggy, affecting fit and comfort. Skin conditions were reported by some, attributed to extended wear. Many developed a preference for the powered air purifying respirator as a result. However, as patient volume and demand for this resource may potentially grow, the PAPR may become a scarce resource, leaving clinicans and other caregivers with challenges in both supply of N95's (we experienced resupply difficulties) and comfort and endurance in providing patient care.
Posted 10/15/09 at 3:23 pm
really good
Posted 10/15/09 at 9:40 pm
From training and experience using both filtering face masks and powered air purifying hoods in controled medical settings and austere environments, I have come to some conclusions. Sometimes one type will work better than the other.
FFMs have the advantage of portability and easy access. Use in situations where noise or commotion exists, I suppose both types of protection will limit it's wearer being heard, but wearing a FFM, the wearer's face and therefor facial expression is hidden. This can be scary for children being treated. I suppose PAPRs, while allowing facial recognition, may be just as alarming to patients.
In hot or humid conditions FFMs can degrade quickly and become hard to breath through. I find vented ones last longer and are easier to breath through. These are more expensive than non-vented FFMs so find their availability scarce.
In later environment PAPRs may last longer, be much easier to breath with, and be cooler, but also cost more.
Will Hill RN
Posted 10/15/09 at 10:05 pm
I just want to know, in outpatient settings, without invasive procedures, can a droplet mask be utilized as opposed to the N95 for protection.
Posted 10/16/09 at 9:45 am
This guidance applies to healthcare personnel working in the following settings: acute care hospitals, nursing homes, skilled nursing facilities, physician's offices, urgent care centers, outpatient clinics, and home healthcare agencies. CDC continues to recommend the use of respiratory protection that is at least as protective as a fit-tested disposable N95 respirator for healthcare personnel who are in close contact with patients with suspected or confirmed 2009 H1N1 influenza.
Careful attention to elimination of potential exposures through engineering controls and administrative controls will reduce the need to rely on PPE, including respirators. This is an especially important consideration during the current year, when shortages of respirators have already been reported by many healthcare facilities.
Healthcare facilities will want to use a multi-level approach, called the hierarchy of controls, that includes both administrative controls and engineering controls to eliminate sources of infection and prevent transmission within their facility.
To ensure a comprehensive infection control strategy, healthcare facilities will want to:
Posted 10/19/09 at 11:10 am
buenos dias, me parece muy interezante este articulo sobre el sistema de proteccion para LA TRASMISION DEL VIRUS H1N1, YA QUE EN NUEWSTRO PAIS EXISTE MUCHOS MITOS SOBRE EL USO DELAS MASCARILLAS.
Posted 10/16/09 at 3:41 pm
As an IH professional, I can attest to the difference in the fit and quality of effectiveness between surgical masks and N95 filtering facepieces. The technology is fantastic and I enjoy inspecting the research that is available.
However, I am in strong disagreement with the aspect of requiring actual qualitative fit testing for each healthcare worker wearing N95 PPE. The actual 'fitting' of the mask is, in my opinion the least effective aspect of a respiratory program that deals with N95's.
I think a stronger emphasis should be put on the educational portion and leave the 'fit testing' for the rubber seal PPE (SCBA, half/full mask, etc).
Definitely there is more research and work to be done.
Posted 10/16/09 at 5:37 pm
What I see is, change those things often,fit was the issue for me, moisture, getting one to last 2-hrs, field dirt, millcleaning, who would know how much still would get by,doing a warm saline rinse,and couphing up what you can.
Don't save, or reuse one, or share one, eye protection is needed for what I was doing too,canister type respirator ok, if you don't bump, and disloge one of your filters, Point to take out is, tools made to help can fail,or not be fit for the task, liability, is your own health at risk.
Posted 10/18/09 at 8:24 pm
This study found that the difference in protection between surgical mask and N95 respirators are not statistically significant. What is your opinion regarding this study?
http://jama.ama-assn.org/cgi/content/full/2009.1466
Posted 10/20/09 at 12:48 pm
Thank you for your question. Randomized controlled trials such as this one [Loeb et al. Surgical mask vs. N95 respirator for preventing influenza among health care workers. JAMA 2009; 302(17): (doi:10.1001/jama.2009.1466)] are very important for documenting the effectiveness of interventions. This study, the first of its kind, examined the impact of assigning nurses to use surgical masks or N95 respirators. It did not find a statistically significant difference between groups in incidence of developing laboratory changes suggesting influenza infection (50/212 in the surgical mask group vs. 48/210 in the N95 group, p = 0.86). In both groups, most of these laboratory changes represented 4-fold increases in titer of serum anti-influenza antibody over the course of the study (44/212 in the surgical mask group vs. 44/210 in the N95 group).
Because symptomatic disease was rare, the study had limited ability to evaluate the effect of surgical mask vs. N95 respirator on clinically significant disease. However, influenza-like illness tended to be lower in those using N95 respirators (9/212 in the surgical mask group vs. 2/210 in the N95 group, p = 0.06) and fever was significantly less frequent in the N95 group (12/212 in the surgical mask group vs. 2/210 in the N95 group, p = 0.007). Thus, the study findings were not consistent across laboratory outcomes on one hand, and clinical outcomes on the other.
Many nurses in both arms of the study were exposed at home to spouses, roommates, or children with influenza-like illness. It is unclear whether cases of influenza observed in the nurses resulted from work or home exposures.
In summary, this study is an important first step. The authors are to be congratulated for taking on such a difficult problem. However, the study does not definitively resolve the ongoing controversy of when to use surgical masks and when to use respiratory protection to prevent transmission of influenza. More studies are needed with better power to address clinically significant disease as an outcome. Also, as more studies become available, it will be possible to assess coherence of results across multiple studies and even to pool data from multiple studies for meta-analysis. Although difficult, this research continues to be greatly needed.
David Weissman, MD, is Director of the NIOSH Division of Respiratory Disease Studies.
Posted 10/26/09 at 10:41 am
Echoing Jim's comment (11) above: education is key. In a true crisis, there would be a mask shortage. Experienced users, and new users without fit kits would not be able to find testing kits (or odorant refills).
Hasn't NIOSH or OSHA developed interim guidance on non-fit test methods, maybe for Katrina or WTC cleanup?
Posted 10/20/09 at 1:44 pm
One of the repeated concerns relayed to my state agency is that N95 respirators are not available or there is a considerable back-order for their respective N95 respirator. Many healthcare institutions insist that the only respirator they can purchase is an FDA approved respirator.
There are multiple respirators that are NIOSH approved, however, there are limited N95 respirators that are both NIOSH and FDA approved. Does NIOSH have any supporting documentation to assist with educating or providing guidance to the healthcare industry regarding the difference between a NIOSH approved and FDA approved respirator? This may alleviate "supply and demand" issues and may assist healthcare providers with choosing alternate respirators when the NIOSH/FDA approved respirators are in short supply or unavailable.
Posted 10/21/09 at 3:09 pm
The Interim Guidance on Infection Control Measures for 2009 H1N1 Influenza in Healthcare Settings, Including Protection of Healthcare Personnel recommends isolation precautions that incorporate the use of Standard Precautions as well as respiratory protection for healthcare personnel who are in close contact with patients with suspected or confirmed 2009 H1N1 influenza. CDC continues to recommend the use of respiratory protection that is at least as protective as a fit-tested NIOSH-approved, disposable N95 respirator for these instances. Standard Precautions include the use of gowns along with eye protection for any activity that might generate splashes of respiratory secretions or other infectious material. A faceshield is one form of eye protection that can be used in conjunction with a NIOSH-approved N95 respirator for protection during for splash-generating activities.
The FDA provides guidance to the healthcare industry regarding the difference between a NIOSH-approved and FDA-approved respirator on their website.
Posted 10/26/09 at 10:57 am
A somewhat frivolous question, but seasonal also. Will decorating the N95 masks with colored markers compromise their effectiveness?
Posted 10/22/09 at 12:47 pm
NIOSH-approved respirators go through a rigorous testing and certification process. Alterations to a respirator, including decorating with ink or paint, can be detrimental to the respirator's performance and may void the NIOSH certification.
Posted 10/26/09 at 10:57 am
As #13 commented,
"This study found that the difference in protection between surgical mask and N95 respirators are not statistically significant. What is your opinion regarding this study? http://jama.ama-assn.org/cgi/content/full/2009.1466
I would like to see a response to this as well. I work as a RN in a large acute hospital setting and am being told by my hospitals adm. that we are to use surgical masks - not N95 respirators. This decision was supported when the recent study regarding the difference in protection between surgical masks and N95's was published in Oct in JAMA. I believe OSHA and CDC are not looking at $ signs when making reccomendations as hospitals are. My feeling is - if hospitals want HCWs to care for infected pts, then they need to step up to the plate and protect those HCWs.
Please respond on the study in question.
Posted 10/26/09 at 12:37 am
Please see the response to #13 above.
Posted 10/26/09 at 1:02 pm
Because N 95's are in short supply, is it possible for the same nurse to re-use the 1860 N 95 3M mask throughout their shift? If so, what is the best way to store the mask-is a sealable plastic bag acceptable or another receptable that would maintain the shape of the mask?
Posted 10/26/09 at 11:34 pm
In the setting of supply shortages, facilities may need to consider extending the use of each respirator. There are two resources available on the NIOSH web page, NIOSH Safety and Health Topic: Occupational Health Issues Associated with H1N1 Influenza Virus (Swine Flu) (http://www.cdc.gov/niosh/topics/H1N1flu/) that address the possibility of extending the use of respirators similar to the scenario you describe.Questions and Answers about CDC’s Interim Guidance on Infection Control Measures for 2009 H1N1 Influenza in Healthcare Settings, Including Protection of Healthcare Personnel (http://www.cdc.gov/H1N1flu/guidance/control_measures_qa.htm) provides considerations for extending the use of each respirator by wearing the respirators for multiple serial patient encounters, as long as the respirator has not been removed and re-donned between encounters.Questions & Answers Regarding Respiratory Protection for Infection Control Measures for 2009 H1N1 Influenza among Healthcare Personnel (http://www.cdc.gov/h1n1flu/guidance/ill-hcp_qa.htm#reuse) provides considerations for extended use as well as respirator re-use, where the respirator is removed and re-donned between patient encounters. Because extended use across multiple patient encounters is of uncertain safety with respect to infection control, these alternatives should only be considered in the event of significant supply shortages/disruptions. In general, extended use (i.e. wearing over multiple encounters while minimizing touching, removing, or re-donning between encounters) would be favored over re-use because it is expected to involve less touching of the respirator and face. Consultation with the facility's infection control experts should be sought in making decisions regarding the most appropriate and feasible personal protective equipment to protect workers from influenza if required by respirator shortages.
The following information comes from the CDC Questions & Answers Regarding Respiratory Protection for Infection Control Measures for 2009 H1N1 Influenza among Healthcare Personnel (http://www.cdc.gov/h1n1flu/guidance/ill-hcp_qa.htm#reuse) .
If extended use practices are implemented as a means to extend respirator supplies, measures should be taken to reduce contact transmission, including:
If re-use is chosen as a strategy to increase availability of respiratory protection, the following should be considered to minimize risk of transmission:
- Discard disposable N95 respirators following aerosol-generating procedures.
- Discard disposable N95 respirators contaminated with blood, respiratory or nasal secretions, or other bodily fluids from patients.
- Disposable respirators must only be used and re-used by a single wearer.
- Do not re-use a disposable respirator that is obviously contaminated, damaged or hard to breathe through.
- Consider use of a face shield over a disposable N95 respirator to prevent surface contamination.
- Store the respirator in a clean, breathable container such as a paper bag between uses.
- Avoid touching the inside of the respirator.
Wearer should perform hand hygiene with soap and water or an alcohol-based hand sanitizer before and after touching a used respirator.Posted 10/29/09 at 9:51 apm
A reader of my blog, www.oshahealthcareadvisor.com, asks:
Posted 10/27/09 at 4:29 pm
Surgical masks are not evaluated on their ability to maintain their protective capabilities when exposed to moisture buildup from coughing, sneezing, talking, etc. We are unaware of any published studies that evaluate the loss in protection over time in either experimental or realistic settings.
Posted 10/29/09 at 9:52 am
I have to disagree with this sentence in your otherwise useful blog entry:
Fit is a measure of facepiece to face seal leakage only. All other sources of leakage are assumed to be essentially zero. 'Fit' is measured in the negative pressure mode only. Total inward leakage can be affected by positive vs. negative pressure. 'Fit' is not.
Posted 10/28/09 at 10:52 am
Thank you for your comment. We have edited the sentence to read: "Negative pressure respirators inherently offer less protection than positive pressure respirators, because inward leakage occurs more easily in the former."
Posted 11/2/09 at 9:38 am
Jerome M. Hauer is calling for release of a "FDA-licensed anthrax vaccine, as of August 2009. (See the FIREHOUSE Forum, page 16.)
H1N1 is viewed as not as deadly as H5N1, per general HCW consensus. However, the H1N1 flu-mist vaccine is commonly viewed by the general public as hazardous.
The US public is not wearing surgical masks or N95 Filtering Facepiece Respirators (FFR), as of 1705hrs today.
The three types of common anthrax are found on many "third- world desert floors". Contamination avoidance techniques which involve the donning of some type of respirator/gas mask with dermal protection and daylight UV wavelengths keep operators "safe" in those third world combat environments. Integrated NIOSH-approved P100 filtration media have "indefinite use life" inside serviceable hardened air-purifying canister housings, provided they stay mechanically intact.
The actions of Health Care Workers (HCW) taking a NIOSH-approved N95 FFR out of its "ready to use package", inspecting it, donning it, wearing it, doffing it, and disposing it or re-using it, has now gotten the attention of the medical science community regarding efficacy of use in SARS, Avian H5N1, and H1N1 contagion outbreaks. Environmental workers cleaning up spores in congressional offices relied on many types of PPE, one of them being the NIOSH-approved PAPR, to protect their breathing zones, with only sparse use of N95 FFR
NIOSH-approved respirators offering "CBRN protection" have captured years of "best practice science" and user survival techniques into many respirator technology platforms whether they be SCBA, APR, PAPR, APER, or loose fitting PAPR. NIOSH-approved N95, N99, N100, R95, P95, P99, or "P100" filtering facepiece respirators do in fact "stop"-filter-out particle sized contagions along a defined air-pressure boundary, from entering the breathing zone. However the safety of the wearer is more about how trained the wearer is in using the respirator with interfacing PPE; what type of vaccinations the wearer currently has viable in his/her physiology; and what "dose" is actually recieved....than how the respirator technology is actually performing regarding "human face-to-faceblank" total inward leakage (TIL), faceblank and seal slippage, assigned protection factor repeatability data, workplace protection factor data, or proprietary use technology designed to capture the multitude of facial anthropometrics that are evolving in the human species.
If you are symptomatic with H1N1 or any type of biological contagion, stay home, get well, and if available, wear a FDA-cleared surgical mask for your own self preservation and the preservation of your loved ones. If you are a HCW charged, or confident enough, to enter a H1N1 or any other type of biological aerosol contagious patient room, at the minimum wear a FDA-cleared/NIOSH-approved FFR certified to at least a NIOSH-N95 filter series and efficiency level.
Most responders would rather not wear a respirator, but realize that wearing a respirator does in fact reduce their chances of gaining an acute lethal dose, or a chronic lethal/non-lethal handicapping dose. HCW should take heed and look at the "biological species indicators" around the globe and apply best practices that are the most beneficial to the survival of their local "customers/patients/stakeholders/warriors/responders and workers".
Posted 10/29/09 at 8:10 am
Would someone please comment on the BioMask made by Filligent and the prospects for getting it NIOSH approved and available in the USA?
Posted 11/5/09 at 5:08 pm
The Filligent BioMask is not a NIOSH-approved respirator. To become certified as an approved respirator, the respirator must meet the all minimum requirements of the approval regulations in Title 42 Code of Federal Regulations, Part 84. Full details can be found at the NIOSH respirator website. Seeking NIOSH approval, manufacturing to quality standards, and distribution is the responsibility of the manufacturer.
The NIOSH approval process does not include evaluation of claims of killing or inactivation of germs, viruses, or other biological agents for the prevention of disease. The Food and Drug Administration (FDA) evaluates such product claims and issues clearance to advertise those capabilities for products that are determined to have demonstrated efficacy in the ability to prevent disease. Seeking FDA clearance is the responsibility of the manufacturer.
Posted 11/13/09 at 3:22 pm
Thank you, this is a very well considered article - and very helpful to provide to those healthcare workers who do not understand the difference between protection for the patient (mask) and protection for the wearer (respirator).
Would appreciate a future study analysis of appropriate respiratory protection for laser users. Because the FDA allows vendors to market surgical masks as 'laser masks'...healthcare workers often believe, with a false sense of security, that their 'laser mask' is actually protecting them from 'laser plume'. From an Occupational Health & Safety perspective, primary control, is of course, an engineering control, such as a smoke evacuator. However, for years, many HCWs believe that, for example, a 'Kimberly Clark' 'Laser Mask' is all they need. A NIOSH statement on this matter would be appreciated...especially when many of the vendors selling so called 'Laser Masks' actually offer a more protective NIOSH certified N95 respirator in their product line, but because the general mask is labelled 'laser mask' the HCW is convinced that this is the better choice.
Posted 11/6/09 at 3:49 pm
If proper engineering controls are not in place, a surgical mask will not provide adequate protection from laser plume. On the NIOSH National Personal Protective Technology Laboratory homepage you can download "Guidance and Resources for Smoke in the Operating Room (zip file)" which is located under the "Healthcare Workers" section of the page. The hierarchy of controls is explained, and several engineering control recommendations are provided. The resources also state that [in the PowerPoint presentation from March 2007: Final_NIOSH_Smoke_In_OR_26Jan07 located in the zip file] N95 Respirators or Surgical N95 Respirators are to be used until effective Engineering Controls are in place.
Posted 11/9/09 at 2:35 pm
I have heard that there is an "emergency" exception to the fit testing requirment for N95 respirtors. Is this true, and if so, what is the specific authority? What constitutes an emergency for purposes of this exception? Thanks.
Posted 11/9/09 at 12:55 pm
No, there is no emergency exception to the fit testing requirement. OSHA recently issued a compliance directive for health care workers. In the OSHA News Release from November 20, 2009, it prescribes: "Where respirators are required to be used, the OSHA Respiratory Protection standard must be followed, including worker training and fit testing. The directive also applies to institutional settings where some workers may have similar exposures, such as schools and correctional facilities." The full text of the News Release and the Directive is available at:
http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=NEWS_RELEASES&p_id=16749
Posted 11/20/09 at 2:12 pm
Dear colleagues:
As an infection control officer (physician) in a hospital of a poor nation, I am faced with limited supplies of N 95 and even surgical respirators. The hospital where I just started to work was "suddenly" ordered by the Minister of Health to start managing H1N1 patients. It is a 500 bed multi specialty hospital with a huge daily outpatient load. ER and Outpatient layout is not designed completely separate patients who need isolation from the rest of the patients. The only room available as an isolation room in the ER, for example, is two rooms inwards. Patients will inevitably pass by "regular" patients and rooms before being isolated and examined.
I know that so far "air borne" transmission of H1N1 is not believed to occur, but it cannot be totally excluded. Ideally, I believe, everyone in the potential path of an H1N1 patient needs an N 95 respirator, something I cannot provide.
My question is: How can I maximize the use of N 95 respirators and surgical (setting priorities)? If reused, what precautions are needed regarding the N 95 respirator during reuse and storage?
Thank You
Posted 11/9/09 at 11:06 pm
Please see the response to comment 18 above.
Posted 11/12/09 at 10:56 pm
Is there any FDA approval (510k) necessary for n95 respirators for use by the general public as opposed to operating room personel. (other than Emergency Use Authorization). If so, which brands have such clearance?
Posted 11/15/09 at 2:00 pm
FDA approval is not needed for N95 respirators used by the general public or for N95s used by healthcare personnel to reduce exposure to hazardous particulates in a patient care setting. However, N95s are not intended for use in exposure settings where the performance of a surgical mask to maintain a sterile field is required.
Posted 11/18/09 at 2:43 pm
I am a nurse working in Alaska in a pressurized fixed wing aircraft. The duration of our patient care time often exceeds 4 hours. During our transports we are frequently exposed to wind, rain, and variable temperatures. I read the comments regarding moisture and effectiveness of N-95 masks with interest. I am also interested to learn more regarding the interface of the mask to the face and impairment of adequate fit. As a male I am curious at what point facial hair growth impacts this seal.
I have two questions:
1. Are you aware of any information regarding the use of PAPRs for healthcare PPE in a pressurized aircraft.
2. For men working in healthcare or EMS with long shift length sometimes exceeding 12 hours how do you suggest ensuring adequate mask to face interface for an appropriate seal or do you suggest a PAPR.
Respectfully,
Rick Janik RN, BSN, CEN
Posted 11/15/09 at 5:40 pm
We are not aware of any studies that investigated the use of Powered Air Purifying Respirators (PAPRs) in pressurized structures. We do not see a reason why a PAPR would not function as designed in a pressurized structure, such as an aircraft, since the respirator should not be placed in a differential pressure due to the pressurization. If a PAPR is chosen for work in this scenario, the respirator manufacturer should be consulted to verify if there are any performance issues in that environ with the model PAPR under consideration.
Paragraphs (g)(1)(i) and (g)(1)(ii) in OSHA's 29 CFR 1910.134 are intended to ensure that facial hair is prevented from interfering with the facepiece seal or valve function. We are unaware of any interpretive OSHA compliance or NIOSH policies defining a time duration between shaves or length of "stubble" or beard growth that would be prohibited. Although the growth and beard density varies among individuals, generally, a one-day's growth of facial hair is deemed acceptable to avoid interfering with the facepiece's ability to seal to the wearer's face.
Posted 11/23/09 at 2:39 pm
I am an Infection Control coordinator at a Rehab hospital. We usually do not admit patients to our hospital with Influenza, but if we would suspect they were symptomatic with ILI, if severe enough they would be sent out to acute care. If they were not severely sick, they would stay, but the therapy would need to be limited, possibly confining them to their rooms.
We discussed our protocol to implement for H1N1 and we are running into issues, i.e., we do not have AIIR nor do we have a respiratory protection program in place. We now are attempting to comply with the new CDC recommendations for use of N95s, but it is very difficult for us, as a rehab, to implement a protocol for the type of services we provide. We do not fit test either. Our psyiatrists have shared with me the JAMA article, and I have several other pieces of literature on this controversy of N95s vs. surgical masks. They think surgical masks will do. I am attempting to create a new policy to add to our pandemic flu policy, but have come to a standstill. I just don't feel comfortable with not following recommendations, but how do you implement these recommendations in a rehab type setting??? Thanks for any advice.
Posted 11/20/09 at 1:31 pm
Thank you for your question. We appreciate the challenges that you describe. We also appreciate your desire to protect both your workers and your many fragile rehabilitation patients from transmission of 2009 H1N1 influenza.
In your question, you mention that your rehabilitation hospital does not have airborne infection isolation rooms. This should not be an issue for you, since the CDC guidelines recommend use of such rooms only as possible for aerosol-generating procedures. "As possible" refers to the fact that cardiopulmonary resuscitation and endotracheal intubation are two of the procedures listed in the guidelines as aerosol-generating.
The CDC guidelines do recommend that healthcare personnel in close contact with suspected or confirmed 2009 H1N1 cases use respiratory protection at least as protective against inhalation of small particulate aerosols as disposable N95 respirators. This recommendation does apply to your rehabilitation hospital. Hopefully recommendations provided in the respiratory protection questions and answers documents produced in association with the guidelines will help in implementing the recommendation with as little impact on your operations as possible:
Because there is substantial evidence that influenza may be transmitted over short distances by small particulate aerosols, a recent Institute of Medicine report recommended use of N95 respirators in a fashion similar to that recommended in the CDC guidelines. Because surgical masks do not provide protection against small particulate aerosols, the CDC guidelines only recommend their use by healthcare personnel at lower risk from influenza if supply issues make true respiratory protection unavailable. In many cases, personnel can be assigned to a lower risk category 14 days after vaccination for 2009 H1N1 influenza.
For a variety of reasons, the JAMA article mentioned in your email (Loeb et al., 2009) is not sufficiently definitive to alter the CDC recommendations. In particular, on reviewing the paper you will note that its conclusion is based on proportions of nurses in the two study arms who had 4-fold increases in anti-influenza titers. However, very few nurses in the two study arms actually developed clinical illness. Among those nurses with clinical illness, "influenza-like illness" (p=0.06) and fever episodes (p=0.007) were less frequent in the N95 group. For a more detailed discussion, please see the response to comment 13 above.
We hope this information is helpful to you.
Posted 11/23/09 at 2:44 pm