- capture particles in the air, such as dusts, mists, and fumes
- do not protect against gases or vapors
- generally become more effective as particles accumulate on the filter and plug spaces
between the fibers
- filters should be replaced when user finds it difficult to breath through them
(see Selection Criteria for Particulate Filters)
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- are normally used in atmospheres that contain hazards of both particulates and gases
- have both particulate filters and gas/vapor filters
- may be heavier
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- are normally used when there are only hazardous gases and vapors in the air
- use chemical filters (called cartridges or canisters) to remove dangerous gases or
vapors
- do not protect against airborne particles
- are made to protect against specific gases or vapors
- provide protection only as long as the filter's absorbing capacity is not depleted
- the service life of the filter depends upon many factors and can be estimated in various
ways
(see Respirator Change Schedules)
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