As we publish this edition of HETI Horizons, the world is in the midst of a global pandemic from COVID-19. Many aspects of daily life have changed. Terms such as “social distancing” and “self-quarantine” have become a part of our everyday lexicon. Another thing that has changed is the proliferation of retail, food service and other deemed essential workers wearing respiratory protection while interfacing with the general public.
The author of this newsletter was more than a bit surprised when he was handed his morning coffee by an employee wearing a full-face respirator at the drive-through! After a brief discussion with the employee, it was clear that the respirator was not only the incorrect type for the hazard (airborne transmission of COVID-19); but it was neither furnished by her employer nor was it provided in compliance with Occupational Safety & Health Administration (OSHA) regulations governing respirator use in the workplace found in 29 CFR 1910.134.
Types of Respiratory Protection
Air-purifying respirators (APRs) remove contaminants in the air that you breathe by filtering out particulates (dusts, metal fumes, mists, etc.). Breathing in air creates negative pressure, which draws outside air through the filter and removes/reduces airborne contaminants of concern. Because of this inherent mechanism of action, if the wearer has an underlying medical condition that affects lung function or has diminished lung capacity, these types of respirators may very well present a more significant hazard than what the user is trying to protect against.
The most basic type of respirator in this class are often referred to as “dust masks”, “filtering facepieces” or “N95 masks”. They are designed to fit snugly against the face to create a tight and proper fit, or seal, between the respirator and the wearer’s face. This barrier, when utilized and sized properly, will not allow contaminants to enter. Masks often have a bendable metal clip incorporated into the nose bridge to be molded across the wearer’s nose. Some masks will have exhalation valves as well, so you do not exhale through the mask filter. [NOTE: An N95 mask captures 95% of particles 0.3 microns or larger. The COVID-19 virus is very small, but attaches to wet mucous and skin cells. So an N95 works well to capture these particles.]
Other APRs purify air by adsorbing gases or vapors on a sorbent (adsorbing material) in a cartridge or canister. They are often made of plastic and/or rubber, are tight-fitting and are available in several forms, such as:
- Half-face mask (covering the face from the bridge of the nose to below the chin)
- Full facepiece (covering the face from above the eyes to the forehead area to below the chin). These respirators also protect the eyes.
Because filters capture particles, caution must be exercised to always check that these filters are not clogged – making it more difficult for air to pass through. Cartridges can also become “full” or saturated – causing the respirator to stop working and “breakthrough” to occur (meaning gases or vapors will leak through the cartridge). Both cartridges and filters must be replaced on a regular basis by using the manufacturer’s recommendations (usually determined by using warning properties or end-of-service indicators).
There are different classes of particulate filters, depending on the particulate material. They are also classified based on levels of oil resistance and filter efficiency. Oil can break down certain types of filters; so it is always important to know the materials and to select the right cartridge for the particular respirator. Any of these main categories of masks will protect to some degree against COVID-19:
- N series (not resistant to oil) may be used in any atmosphere where there is no oil particulate.
- R series (resistant to oil): may be used in any atmosphere where there is no oil particulate, or up to one shift (eight hours of continuous or intermittent use) where there is oil particulate present.
- P series (oil-proof): may be used in any atmosphere, including those with oil particulates.
It is important to note that surgical masks are not tight fitting and are not covered under OSHA’s Respiratory Protection Standard (29 CFR 1910.134). They offer some degree of protection from particulates and mists; however they do not rely on a tight fit between the face and the respirator itself. So contaminants can enter around the mask or through the cloth into the breathing zone. While these surgical masks are somewhat effective, they are less effective than N95s.
Another type of respiratory protection is supplied-air respirators (SARs) – which supply clean air from a compressed air tank or through an airline. Types of SARs include:
- Self-contained breathing apparatus (SCBAs)
- Airline supplied-air respirators
Yet another type of SARs are powered air purifying respirators (PAPRs). These respirators incorporate a hood, shroud or helmet design which is supplied air via an external fan that draws in contaminated air through a filter or cartridge and supplies positive pressure to the hood/helmet. The positive pressure prevents contaminants from entering the breathing zone. These types of respirators often offer a high level of protection coupled with wearer comfort and are preferred in certain healthcare situations.
Respiratory Protection Standards and Considerations
Each respirator type has an assigned protection factor (APF) – designated by OSHA based on a determination of how well a respirator/filter combination will protect an individual from external contaminants. An APF is an estimate of the level of protection a respirator provides and is used to select the appropriate class of respirators for the necessary level of protection.
The higher the APF, the more protection the respirator is designed to provide. An APF of 10 means that no more than one-tenth of the contaminants to which the worker is exposed will leak into the inside of the mask. An APF of 100 means only one percent leakage. Dust masks offer the lowest level of protection and have the lowest APF. SCBAs with full mask and pressure demand air supply offer a high level of protection with an APF of 10,000. Choosing the proper respirator depends in part on the airborne concentration of the contaminant of concern.
Obtaining a proper respirator fit is vitally important. The wearer should not have a beard or unshaven facial hair, as the hairs will not allow for a proper fit. All respirators require a fit-test to demonstrate the person is using it correctly. These fit-tests use a bitter solution, irritating smoke or other approved methodology to assure a proper fit. Prior to fit-testing, intended respirator users must be evaluated by a licensed healthcare professional (LHP) in order to assure that no underlying respiratory conditions are present that may make wearing the respirator a hazard.
This means that – in an occupational setting – users must be medically cleared prior to using the respirators…then fit tested. All workers that wear tight-fitting respirators must also have formal training in respirator proper use, donning/doffing, limitations, maintenance, and storage requirements – as mandated by OSHA. The only exemption to the medical clearance requirement is providing dust mask type respirators to employees on a strictly volunteer basis. In this situation, intended wearers of this type of device need only to sign the document provided in Appendix D of the OSHA Standard (29 CFR 1910.134). Providing other “non-dust mask” types of respirators – such as half-face, full-face and SARs – require medical clearance in all cases.
EHS Services from HETI
HETI’s environmental health & safety professionals are available to assist clients with an array of EHS issues and concerns. Whether the need is for workplace exposure assessments, respiratory protection selection and fit testing, training, or simply addressing questions, we are here to help.