Choosing the right filter for a reusable respirator depends on the job at hand and what types of contaminants workers might be exposed to. This article shares what factors to consider when choosing filters.
What can filters help protect against?
Filters are designed to capture airborne particles, and not gases or vapours. Particulates come in different forms and can pose different levels of risk. Some of the most common forms of particulates include:
- Dust – dry particles that exist naturally or are mechanically produced. E.g. Sanding during woodworking creates sawdust, while cutting cement during construction work can create silica dust.
- Mist and aerosols – liquid droplets that are suspended in the air. E.g. Aerosol paints used in spray painting produce mists.
- Bioaerosols – living or non-living airborne particles of biological origin. E.g. Bacteria, fungi, and viruses, which are considered living, can be found in healthcare settings, waste management and composting facilities, as well as in the food and beverage industry. Non-living bioaerosols can include pet dander, pollen, and saliva.
- Fumes – aerosol-produced when a material in the gaseous phase condenses to form a solid. E.g. Welding work, which includes heating of metals, creates welding fumes. Torch cutting also produces fumes.
- Fibres – solid particulate where the length is many times greater than its width. E.g. Common examples include asbestos, fiberglass, and carbon fibres.
How are filters classified?
Filters are classified by their rating and efficiency according to NIOSH.
The workers wearing the filter need to know whether there is oil present in the air in order to choose the correct class of filter. Filters are classified by the following series:
• N = no oil
• R = oil resistant
• P = oil proof
Filter efficiency is also dictated by NIOSH and the efficiencies are either 95%, 99% or 100%. For example, a filter that is rated 95 means that 95% of the particulate will be filtered out. Refer to the results of your hazard assessment to determine the appropriate filter efficiency for your job.
Unique filter features
3M has a variety of filter options for reusable respirators, including:
• Carbon layers – specially designed carbon layers help provide relief against nuisance levels of organic vapours which is useful for reducing odour. (3M™ Particulate Filter, 2097)
• Advanced particulate filter – designed with three layers of filter media versus the traditional five to allow the wearer to experience better breathability and a lighter weight without compromising protection. Advanced particulate filters also incorporate netting construction to help increase durability of the filter. (2200 series)
• Plastic encasement – 3M™ Particulate Filter, 7093 are encased in a hard shell, making them ideal for applications with flying debris, including grinding and spark-producing activities). These filters are also used in the abatement market as the filter is protected from decontaminating water spray showers. Lastly, the filter size and design are small enough to fit beneath a welding helmet or face shield (7093 series)
Why the occupational exposure limit (OEL) matters
The OEL is the upper limit on the acceptable concentration of a hazardous substance in workplace air for a particular material or class of materials. The OEL is set by a national authority and is enforced by legislation to protect worker health.
To determine the OEL of a workplace, air sampling must take place. Air sampling is a process that measures the airborne levels of contaminants in the workplace. Typically, a third party company or trained industrial hygienist will conduct air quality sampling. Based on the results of the sampling, the level of respiratory protection needed would then be determined.
How the assigned protection factor (APF) affects respiratory protection
APF is the level of expected protection for a particular respirator model, which can vary by province. For example, half facepiece respirators have an APF of 10. This means that when the respirator is worn with the correct filters, the wearer is protected up to ten times the occupational exposure limit. A full facepiece reusable respirator can provide an APF of 50, which can provide protection up to fifty times the OEL. However, you may need to perform a quantitative fit test to obtain the higher protection factor and you may never exceed the Immediately Dangerous to Life or Health (IDLH) concentration, even if you are under fifty times the OEL.
For more information on which type of filter is best for the application at hand, please reach out to a representative by filling out the form below.
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