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Engineering Controls Database

Reducing Worker Exposure to Hazardous Dust During Tuckpointing

Construction workers are exposed to hazardous dust when grinding or cutting mortar or cement from between the bricks of old buildings. As brick buildings get older, the mortar between the bricks starts to fall apart and needs to be replaced (tuckpointing) to prevent water intrusion into the building. Before replacing the mortar, ½ to ¾ inch of the old mortar is removed by using a grinder. The grinder breaks up the mortar and turns it into airborne dust that may contain crystalline silica. The crystalline silica dust released during tuckpointing operations is very hard to control and dust may be carried throughout the workplace. Workers who use grinders to remove deteriorated mortar between bricks may be exposed to crystalline silica at concentrations up to 100 times the NIOSH recommended exposure limit (REL) of 50 µg/m3
Breathing dust that contains silica can lead to the development of silicosis, a deadly lung disease. In addition, exposure to crystalline silica has been linked to lung cancer, kidney disease, reduced lung function, and other disorders. No effective treatment exists for silicosis, but it can be prevented by controlling workers’ exposure to dust containing crystalline silica.
NIOSH has identified control measures to reduce worker exposure to hazardous dust during tuckpointing. Studies show how an industrial vacuum cleaner attached via a flexible hose to a shroud that partially encloses the grinding disk can reduce silica dust exposure.

Vacuum Cleaners: The choice of a vacuum cleaner depends on the task. The vacuum cleaner should draw at least 10 amps if it is to be used as part of a ventilated grinder system. Although a minimum air-flow rate of about 65 cubic feet per minute (cfm) provides adequate air flow, the objective is to provide an air flow of 80 cfm to achieve effective dust control. A vacuum cleaner with a cyclonic preseparator (cyclone) should be used to keep debris off the final filters. This will enable the vacuum cleaner to maintain an adequate airflow, which will facilitate dust capture and transport. Thus, it is very important to monitor the airflow rate. A vacuum cleaner equipped with a pressure gauge allows the worker to determine whether the airflow rate is too low to be effective. If the vacuum cleaner does not have a pressure gauge, workers can monitor the air flow by checking to see if a dust plume is escaping from around the shroud. The final filter should be a high-efficiency particulate air (HEPA) filter to reduce the chance of releasing dust containing crystalline silica from the vacuum into the worksite.

Hose: A 2-inch diameter hose with a smooth interior and a length of no more than 15 feet provides adequate air flow to capture and transport the mortar dust. The air flow provided by smaller diameter hoses (e.g., 1.5 inch) was far less than that provided by 2-inch diameter hoses. The hose should have as few elbows or turns as possible.

Shroud and Grinder: The exhaust shroud can be purchased separately or as a unit with the vacuum cleaner and hose. The shroud should totally enclose the spaces around the exhaust entry point for the hose. The shroud should have an entry point for the hose of 2 inches to match the diameter of the hose. Some tuckpointing grinders come with an attached shroud.
Uncontrolled mortar removal

Uncontrolled mortar removal

Diagram of mortar removal

Diagram of mortar removal
247-18; 247-20;
mortar removal
tuckpoint grinder
ventilated grinder system
The control noted above was found to reduce silica dust by 5 to 20 times during tuckpointing when compared with studies in which no dust controls were used.