24th March is World TB Day (2)

Face masks and respirators: Personal respiratory protective equipment for TB prevention

As per the CDC, there are three levels of TB infection control in health-care settings.

The first level “administrative controls” should minimize the number of areas where exposure to Mycobacterium tuberculosis may occur.

The second level “environmental controls” should reduce the concentration of airborne TB bacteria in areas where exposure may occur.

The third level is the use of “personal respiratory protective equipment” by persons entering the areas where exposure to airborne TB bacteria may occur.

Personal respiratory protective equipment include face masks and respirators.

  • Face masks are cloth or paper masks e.g. surgical masks, which prevent the spread of micro-organisms from the user to other people by capturing large wet particles near the source (mouth and nose), but it does not provide sufficient protection from inhaling airborne infections.
  • Respirators are special type of closely-fitted mask with the capacity to filter particles 1 micron in size to protect from inhaling infectious droplet nuclei.

The respirator has tiny pores, which block droplet nuclei and forms an air tight seal around the entire edge. On the other hand, a face mask has large pores and lacks air tight seal around edges and therefore do not prevent leakage around the edge of the mask when the user inhales.

N95 masks are particulate respirators and filter particles ≥1 micrometer in diameter with at least 95% efficiency given flow rates up to 50 L/min. But, to be effective, N95 masks must fit the face with less than 10% seal leakage. Adjustable nose clip helps in obtaining a secure seal. All require fit-testing and must be adjusted to the face to provide the intended effectiveness of filtering 95% of particles with mass median diameter of 0.3 micrometers.

They are not designed for children or people with facial hair. Because a proper fit cannot be achieved on children and people with facial hair, so the N95 respirator may not provide full protection.

N95 respirators can be surgical or industrial types. The ones used in hospitals are surgical ones and the one used in the industry are industrial certified and are used in construction and other industrial type jobs that expose workers to dust and small particles.

All respirators must be put on and taken off in an area outside of the contaminated area. Putting a respirator on or taking it off even for a few seconds in a contaminated area can expose the wearer to significant levels of hazards.

All patients with cough (TB suspects on screening) should be provided with simple mask at the reception of a hospital to cover their mouths and noses. They should be advised about respiratory hygiene and cough etiquettes. They should be instructed to cover their mouths and noses when coughing or sneezing.

Use of a face mask does not protect health care workers from TB.

Doctors and other health care workers should wear N95 mask for TB prevention.

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