The Last Line of Defense

The Last Line of Defense

Sometimes PPE is needed to ensure healthy employees.

Respirators are the last line of defense for dust mitigation and filtration through silica and sanding to protect users from respirable crystalline silica. According to OSHA, this fine particle is at least 100 times smaller than ordinary sand granules found at the beach. These particles are formed when cutting, sawing, grinding, drilling and crushing stone, rock, concrete, brick, block and mortar.  

About 2.3 million people in the U.S. are exposed to silica at work. When this form of silica is inhaled, it increases the risk of developing silica-related diseases such as silicosis. Silicosis is an incurable lung disease that can be fatal and typically occurs within 15 to 20 years of working while exposed to respirable crystalline silica. Other respirable crystalline silica diseases include lung cancer, chronic obstructive pulmonary disease (COPD) and kidney disease.  

For respirators, safety standards are put in place to help protect workers from these diseases, which can sometimes be fatal. OSHA requires all respirators on jobsites to be approved and rated by the National Institute for Occupational Safety and Health (NIOSH), the federal agency responsible for testing and approving respirators used in U.S. workplace settings. Each respirator goes through standard tests to qualify the respirator as an air-purifying respirator (APR) and receives a classification.  

What do the NIOSH Ratings Mean?  

Particulate respirators are classified by the filter material (N, R, P) and the protective properties (95, 99, 100). Below are the filter’s Classification when exposed to oils: 

  • N Class: respirators/cartridges are not resistant to oils 
  • R Class: respirators/cartridges are somewhat resistant to oils 
  • P Class: respirators/cartridges are strongly resistant to oil/oil proof  

In this case, we will use the following definition for oil, “Mineral, vegetable, synthetic substance, animal, or vegetable fast that slippery, combustible, viscous, liquid, liquefiable at room temperatures soluble in various organic solvents as ether, but not in water.” 

As mentioned above, particulate respirators are also classified by their protective properties. Here’s a breakdown of 95, 99 and 100. 

  • 95 percent: filters at least 95 percent of the most-penetrating particle sizes 
  • 99 percent: filters at least 99 percent of the most-penetrating particle sizes 
  • 100 percent: filters at least 99.97 percent of the most-penetrating particles (HEPA Filters) 

The Most Common Protection 

N95 filters are the most common, and N95 respirators that are NIOSH-approved have a testing and certification (TC) approval number printed on the respirator for easy identification. N95-rated respirators filter at least 95 percent of airborne particles but are not resistant to oil-based particles. 

Not every N95 mask on the market is NIOSH approved and complies with OSHA jobsite requirements. N95 masks can be identified as NIOSH approved by searching for it on the Certified Equipment List. This list is supplied and regulated by the CDC and gives the user the option to search by TC number. If there are no results found, it is not a valid NIOSH approval number, and it does not meet testing standards to be approved. Depending on the manufacturer, disposable respirators typically have a five-year shelf life, and the date of manufacture and expiration are required on the packaging.  

Additionally, N95 NIOSH-approved respirators will have required specific labeling printed on the facepiece. The most common replica of an N95 respirator is the KN95. The two look very similar, but the KN95 mask is the Chinese standard for air filtrating devices and does not meet the U.S. standard for effectiveness. Both masks filter out 95 percent of the most-penetrating particles, however, the KN95 mask is not regulated by NIOSH. 

Standards and Testing 

Per OSHA, to protect workers exposed to respirable crystalline silica, there are two respirable crystalline silica standards: one for construction, and the other for general industry and maritime. These regulations require contractors to always have approved respiratory protection readily available for their employees. On top of that, every user must undergo medical evaluations and fit testing conducted annually.  

When an employee accepts a job where respiratory protection is needed, or if the user is consistently encountering work where it is required, they must undergo a medical evaluation. First is an online self-evaluation to determine their physical health—standard questions are asked about smoking, physical fitness, asthma, allergies, etc. If they pass the test, they move forward with the fit testing portion. If the employee fails the test, they must go in for a complete physical with a physician or be moved from the jobsite.  

Fit testing of respiratory protection is the next step to ensure employees breathe safely and are protected from silica. These fit tests are conducted annually, and the records are kept in a database for three to five years. Those taking the test must be cleanly shaven, as facial hair creates a barrier from a tight seal around the nose and mouth. Masks must be worn appropriately; whether disposable, half or full fitting, the masks must fit the face snugly.  

There are two types of fit testing, qualitative and quantitative. Qualitative fit testing is more commonly used due to the ease of the test. The test can be administered by anyone who is fit test certified and is conducted by placing a hood over a user with a respirator on. The hood is then filled with an irritant, like Saccharin, Bittrex, Smoke or Isoamyl Acetate. If the irritant penetrates through the mask, the user will begin to cough or taste bitterness, and the mask will be deemed an improper fit. Benefits to this form of testing are that it is cheaper than quantitative and can be administered on jobsites, however this form of testing is subjective. The employee being tested could lie about what they taste or smell, or there could be outlying factors like allergies that disrupt a person's regular breathing pattern.  

Quantitative fit testing is less common and is conducted by a monitor that measures the pressure drop and communicates success through a numerical fit factor. A "fit factor" changes based on the style of the respirator. It determines if it "fits." N95 and half-face masks are judged on a point system up to 200pts, but anything above 100pts is considered passing. Full face masks are measured up to 500pts. This form of testing is that it is the most accurate read-out, but employees will generally have to leave work to go to a third-party clinic to get the test conducted, and it typically costs more to conduct.  

After fit testing is complete, the employee is given a sizing and model card that they must keep on them when working where respirators are required, or some larger companies will upload their employee's fit test cards to OSHA's database.  

User Frustrations  

Even with all these standards, testing and potentially fatal silica-related diseases, we still see a trend of users not wearing proper respiratory protection. If a user's personal protective equipment isn't comfortable, it won't be worn at all. The main frustration with this protection is comfort. Many employees complain about the way a respirator fits, saying the straps become uncomfortable over extended periods of time.  

Another frustration is heat. While working in hot conditions, many respirators do not keep the users cool. Some PPE manufacturing companies provide solutions that keep users cool and comfortable by providing features like a full gasket, ultrasonically welded adjustable straps and a temperature-reducing valve.  

The Bottom Line  

OSHA is committed to keeping workers safe from silica with dust management and extraction but also asks contractors and safety directors to integrate respiratory protection onto their jobsites to ensure that employees are safe and healthy. Workers who need respiratory protection will need to undergo the proper medical and fit testing to ensure they are compliant and adequately protected from harmful silica. These standards and commitment to protection will ultimately help keep employees safe and productive on the jobsite. 

This article originally appeared in the July/August 2022 issue of Occupational Health & Safety.

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