New Computer Program Advances Guidance On Predicting Air-Purifying Respirator Filter Cartridge Service Life

December 22, 2003
NIOSH Update:

Contact: Fred Blosser (202) 401-3749

The National Institute for Occupational Safety and Health (NIOSH) announces new computer software that enables administrators of workplace respiratory-protection programs to consider the effects of relative humidity on the service life of NIOSH-approved organic vapor (OV) chemical cartridges. This software assists program administrators, in workplaces where air-purifying respirators are used, in reducing on-the-job respiratory exposures to potentially harmful organic vapors from a single volatile source, such as an individual paint, thinner, or solvent.

The ambient relative humidity in the environment in which an air-purifying respirator is used or stored is one of the factors that, over time, can cause the sorbent in a cartridge to lose its ability to collect organic vapors from the air breathed in through the cartridge. Collecting the vapors removes them from the air that the respirator user breathes into his or her body. Advances in computational capabilities of personal computers, and verification of the mathematical model through recent research, made possible the addition of this critical factor to the software program that was not included in previous government versions.

The new software program also incorporates factors that were used in previous computer software available from the government. Those factors include, for example, the type of air contaminant against which the chemical cartridge will protect the user, the concentration of the contaminant, the parameters of the cartridge, and the rate at which the user is working.

By using the software, a respirator program administrator can determine when the cartridge is likely to reach the end of its service life or effectiveness; this is the point at which “breakthrough” is likely to occur as the sorbent no longer is able to collect organic vapors at the needed capacity. With that information, the administrator will know when to schedule a replacement of the cartridge.

“Especially in situations when the use of air-purifying respirators may be necessary for hours, knowing when to change the organic vapor cartridge is critical for keeping the user safe and healthy,” said NIOSH Director John Howard, M.D. “By adding in a key factor that was not included in previous government software, program administrators can feel more confident in the schedules they set for changing cartridges.”

The new computer software reflects the concept of government leadership through collaboration with diverse technical organizations. The software resulted from research conducted by Los Alamos National Laboratory (LANL), in conjunction with a partnership by NIOSH, LANL, the Occupational Safety and Health Administration (OSHA), the International Safety Equipment Association (ISEA), the American Chemistry Council (ACC), the Synthetic Organic Chemical Manufacturers Association (SOCMA), the National Paint and Coatings Association (NPCA), and the American Petroleum Institute (API), organized and led by ORC Worldwide. The consortium provided funding for the initial research, and then joined with NIOSH, which provided funding necessary to complete the work.

Further research is continuing on a more sophisticated program that will enable respirator program administrators to determine schedules for changing OV cartridges in environments that contain vapors from more than one volatile source.

The new computer software, “Breakthrough: Single Vapor Beta Version 3.0.0, expiration date December 2004,” will be available shortly as a CD-ROM that can be ordered from NIOSH at 1-800-35-NIOSH (1-800-356-4674). The software is currently available as a download from OSHA’s website at icon. The download includes a digital training video illustrating the use of the program, as will the CD-ROM. For further technical information, contact Gerry Wood, Los Alamos National Laboratory, Mail Stop K-486, Los Alamos, N.M. 87545, email or Jay Snyder, NIOSH National Personal Protective Technology Laboratory, email

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