N95 Masks
3/30/2020
COVID-19 has taken center stage everywhere throughout the country. It’s in the news – just about 100%. It is also the main topic of conversation in restaurants, cafes and coffee houses – well, it would be the main topic of conversation if restaurants, cafes and coffee houses were open.
And because of the COVID-19 outbreak, new words and phrases have crept into our lexicon. Specifically, PPE (for personal protective clothing) and N95 masks. Being an industrial hygienist, I find myself often cringing when I hear newscasters use these terms as it is quite apparent (at least to me) that they really do not have a full grasp of their meaning. This especially true for N95 masks, so I would like to give a detailed description of what these devices are.
To begin, in the world of occupational safety and health (S&H), respiratory protection requirements are specified in the regulation, 29 CFR 1910.134. This regulation (title 29 of the Code of Federal Regulations, Part 1910 (referring to General Industry), Section 134 (Respiratory Protection)) details how respirators shall be selected, used, and maintained (this includes employee training, fit testing and types of respirators). This regulation also makes a reference to how respirators shall be tested so that their ability to protect workers is established. And this reference is location in 42 CFR 84; referring to “Public Heath” (that’s title 42 CFR), followed by “Approval of Respiratory Protective Devices (Part 84). The specific section of this part (84) is 181 (Non-Powered Air Purifying Particulate Filter Efficiency Level Determination): which is within Subpart K (Non-Powered Air Purifying Particulate Respirators). I know that’s a LOT of information that is most likely beyond what any of us really needs or wants to know. But I thought that some of us may want such details. At any rate, there is no quiz!
According to 42 CFR 84, non-powered air purifying particulate respirators are designed for use as respiratory protection against atmospheres with particulate contaminants. They are not effective to control inhalation hazards due to vapors or gases as well as not providing any protection in atmospheres where there is not an adequate supply of oxygen (i.e. atmospheres with an oxygen concentration that is less than 19.5%.
There are three types of particulate filters; N-series, which are restricted to use in those workplaces free of oily aerosols (these are oily particulates – not oil vapors!), and R- and P-series filters; intended for removal of any particulate that includes oil-based liquid particulates. So, if you are working at an oil refinery or other location where oils may be prevalent, the N-type respirator, would not be recommended.
After the alpha designation (N, R or P), comes the numeric classification and are tested to ensure the efficiencies presented below:
- N100, R100, and P100 filters shall demonstrate a minimum efficiency level of 99.97 percent.
- N99, R99, and P99 filters shall demonstrate a minimum efficiency level of 99 percent.
- N95, R95, and P95 filters shall demonstrate a minimum efficiency level of 95 percent.
Every respirator manufacturer must submit twenty respirators of each respirator model for testing. Testing consists of subjecting all 20 units at a continuous flowrate of 85 ±2 liters per minute (LPM); regardless of whether you have an N95 or R99 or P100 respirator. Just to get an idea of this flowrate, according to the Fundamentals of Industrial Hygiene, the typical breathing rate for humans is 5 LPM, while radiological models use 20 LPM.
For N-series respirators, the particulate aerosol is sodium chloride. For R and P units, a dioctyl phthalate (that’s the irritant smoke that is sometimes used for qualitative fit testing for respirators) or equivalent liquid particulate aerosol is used. For N95 respirators, the particulate diameter used in the testing protocol is 0.075 micrometers.
Each of the 20 N95 respirators that a manufacturer submits for testing, is subjected to a 20-minute period and must maintain its 95% efficiency. If any of the 20 respirators fails, the entire product does not pass and therefore cannot be classified as N95.
So, when we wear an N95 respirator, we can feel confident that it will effectively filter out at least 95% of all particulates in the air from entering our respiratory system. And because the testing procedure is more rigorous than our typical breathing rate, evidence has shown that we can get an efficiency that is substantially higher than 95%. As a matter of fact, testing at workplace locations have yielded efficiencies as high as 100%!
However, remember that it is the actual filtering material that is being tested; NOT the efficiency provided by the N95 respirator when worn. In order to ensure a wearer is receiving the appropriate protection, each person must be fit tested. Without a respirator having a proper seal to the users’ face, airflow will bypass the filter and take the path of least resistance; that is, through the openings between the face and respirator.
This is why persons that are on the front lines in today’s corona virus pandemic, such as first responders and those working in hospitals, need to be properly fitted. Recent news has presented unfortunate cases of health care workers succumbing to corona virus and while the specific cause of how these individuals actually contracted this disease cannot be determined, we know that wearing PPE incorrectly can be a major factor.
We all see people walking around in airports and food stores with non-descript disposable masks and N95 units as well as some wrapping their faces in scarfs and other articles of clothing to protect themselves from diseases. Without the being properly fit tested, these articles may help only by reducing particles from becoming airborne due to the wearer’s coughing and sneezing; but will not protect the wearer from inhaling airborne particulate (such as corona virus – which are spherically enveloped particles). On the contrary, those that continuously wear the same filter (or article of clothing) create an unsanitary condition, which can result in causing health concerns other than corona virus.
For this reason, PPE, such as N95 respirators should be worn by those that are on the front lines, where the ability to ensure these units, as well as other forms of PPE, are properly worn. For the rest of us, practicing social distancing, washing our hands often, staying away from others (as best as we can), disinfecting commonly used surfaces (stair bannisters, door handles, etc.) can be very effective to control the spread of corona virus, thereby protecting ourselves and loved ones.
How very little can be done under the spirit of fear