Solution Summary: Respiratory Protection With an Assigned Protection Factor (APF) of 1,000
Exposure to airborne dust, silica, asbestos, and chemical vapors can lead to a variety of diseases and even death. Respirators, when properly fitted and used, reduce the inhalation of airborne contaminants. When engineering controls, administrative controls, and good work practices have been used to reduce the extent of the hazards on a jobsite, respirators can provide additional reduction of risk. This solution focuses on NIOSH-approved respirators with an assigned protection factor (APF) of 1000. This includes powered air purifying respirators (PAPR) with a full facepiece, and supplied airline respirators (SAR) with a full facepiece.
OSHA requires implementation of engineering, administrative, and work practice controls to mitigate airborne hazards, with proper use of respirators being the last layer of protection when additional controls are necessary. OSHA requires respirators to be used as part of a complete and effective respiratory protection program implemented by the employer.
- Engineering controls, work practices, and administrative controls seek to reduce worker exposure to airborne contaminants. Engineering controls remove dust through local exhaust ventilation, tool-mounted vacuums, or wet work. Work practices rely on training, SOP’s, proper clothing, and equipment maintenance to reduce worker exposure to contaminants. Administrative controls minimize worker exposure through scheduling and work assignment rotations. These are discussed in more detail in OSHA’s Technical Manual.
- Respirators are used as an additional layer of protection to reduce worker exposure below the OSHA Permissible Exposure Limit (PEL) for the hazard. The APF tells you up to what level above the PEL a properly fitted respirator will protect a worker. For example, the PEL for asbestos is 0.1 fibers/cc, so a respirator with an APF of 1000 will provide protection in an environment with exposure up to 100 fibers/cc.
- Respirators must be selected based upon the type and extent of hazard present in the work place. A qualified person should assess the worksite risks and follow NIOSH respirator and filter selection logic. OSHA provides an online tool for respirator and filter selection that follows the same logic. Respirators, cartridges, and filters must be certified by NIOSH and a searchable equipment list is available.
- Respirators offer protection against hazards only when partnered with the appropriate filters or cartridges. A HEPA filter will provide excellent protection against airborne particles like silica and construction dust, including nanometer-size particles, but will do nothing for chlorine vapors. Filters and cartridges are hazard-specific, color-coded, and come in combinations to provide protection against multiple threats. Filters and cartridges are brand and style specific and cannot be swapped between non-identical respirators. Filters and cartridges must be changed on a regular basis as determined by the employer’s respirator change schedule.
- Particulate filters are rated by NIOSH based on how well they remove particles from the air. A filter with a rating of 95% efficiency removes 95% of particles at 0.3 µm (300 nm) and research has shown that they are effective with even smaller particles. This is discussed further in the Risks Addressed section below.
- Particulate filters are also rated based on their resistance to oil, which is important because some oil can reduce the effectiveness of the filter. The table below shows the types of filters available. A filter cartridge or filtering facepiece must have the proper designation printed on them to show their NIOSH approval. For example, an oil-resistant HEPA filter cartridge will indicate R100 on the label.
Resistance to Oil
N (not oil resistant)
R (oil resistant)
P (oil proof)
- Medical clearance is necessary when employees are required to wear a respirator for their job. This is discussed in more detail in the respiratory protection program solution.
- Fit testing is also required by OSHA prior to respirator use. While a medical clearance can cover multiple respirator types, fit tests are respirator specific and must be conducted for every brand, size, and style to be worn. Fit testing must be updated at least once per year, after any face or dental surgery, or if the worker experiences a significant change in weight. Fit testing may be qualitative or quantitative.
- During qualitative fit testing the employee performs a set of tasks while exposed to an aerosol (video version). If the user detects the test agent then the test fails and the respirator cannot be used.
- Quantitative fit testing involves the use of a computerized system to determine fit factors during a variety of exercises. The most common quantitative fit testing method uses an instrument that compares the concentration of airborne particles inside and outside the facepiece to determine if the fit is adequate. Leakage from a poor fit is a more frequent route for contaminants to get inside a facepiece than through filter media. In the highly dusty environment of a construction site, this is significant. While the qualitative fit test ends in a pass/fail designation, the quantitative fit test provides an overall fit factor. These fit factors must be higher than the APFs for the respirators. OSHA requirements for fit testing are available online. Any PAPR that seals tightly to the wearer’s face must be fit tested regardless of the mode of operation, but the PAPR fit test is conducted with the blower turned off.
- Employees must also perform a respirator seal check every time they wear their respirator. Seal checks verify that the respirator is adequately sealed to the face.
- Respirators should be cleaned and inspected daily to ensure proper fit and function, with attention paid to checking particulate filters for breaks.
- A PAPR uses a small air pump to force air through the filters or cartridges. This pump is battery operated and carried by the worker on a belt or harness. The filters work the same as with other respirators, but the combination of a full facepiece with air pressure creates the high protection factor. The air pump creates a slight positive pressure under the facepiece. Should the seal around the face fail, the positive pressure will push outward, preventing ambient air from entering the breathing area.
- SARs provide air by either pulling ambient air through an air pump or a compressor or by drawing air from cylinders or bottles. In both cases the air is supplied with an airline to the respirator. This provides the same positive pressure protection as in the PAPR and eliminates the need for battery packs. However, this does limit worker movement to the length of the airline, which cannot be longer than 300 feet (42 CFR Part 84, Subpart J.149) and can create problems for working around obstacles. Additionally, in atmospheres immediately dangerous to life and health (IDLH), OSHA requires an auxiliary self-contained air supply, generally a small hip-worn bottle . This allows the worker to safely exit the work area should the pump or compressor fail or the airline become compromised. In construction, SARs using air pumps and compressors are more common than SARs attached to compressed air cylinders. Constantly changing cylinders on a construction site is usually difficult, although the Grade D air in cylinders is much more carefully controlled. Pumps and compressors must be positioned and operated to avoid drawing in contaminated air and sending it into the facemask of workers. Keeping pumps and compressors away from sources of carbon monoxide (CO), including idling vehicles and gas-powered equipment, is critical.
- In-line air-purifying sorbent beds and filters may be needed to clean the air.
A compressor may be a source of CO if it is oil-lubricated: the oil, if it gets hot enough, can break down into combustion products that include CO. OSHA requires a high-temperature or carbon monoxide alarm or both for this type of compressor.
Examples NIOSH-Approved PAPR and SAR
- Available in small, medium, and large
- NiMH or Lithium Ion batteries
- Face mounted or belt mounted filters
3MTM PowerflowTM PAPR
(Photo courtesy of 3M)
- Available in medium or large
- Constant flow system for worker comfort and protection
- Moisture resistant filters
- Available in small, medium, and large
- Belt mounted filters
- Includes air pump, full facepiece, and 50’ hose
- Oil-less pump creates no CO or oil vapor
- Hose clips over the shoulder to avoid interfering with the work zone
Scott Safety SAR
- Includes personal air flow regulator
- Pump sold separately
- Constant flow design for worker comfort and safety
- Pumps sold separately
Airborne toxic dusts, mists, vapors, and fumes can cause illness or death. Gases, vapors, and fumes can reduce available oxygen, impair judgment, and/or present an immediate danger to life and health. Powered air-purifying respirators (PAPRs) filter contaminants from the air but do not provide breathing air and must not be used in oxygen-deficient or immediately dangerous to life and health environments, which may include confined spaces. Additionally, PAPRs are not reliably effective against some gases, including carbon monoxide. Chronic inhalation of silica and of asbestos dust has been linked to an increased risk for multiple types of cancer, chronic obstructive pulmonary disease (COPD), asbestosis and silicosis. PAPRs, when properly used, can effectively reduce the inhalation of dust. Supplied air respirators (SARs) do provide breathing air from cylinders or from pumps and compressors. Care must be taken with pumps and compressors to be sure they are drawing uncontaminated air. OSHA requires a high-temperature alarm or a carbon monoxide alarms on oil lubricated compressors because of the risk of carbon monoxide being generated by the heat.
How Risks are Reduced:
Well-fitted PAPRs form a tight seal around the face ensuring that air must travel through the filter or cartridge before being inhaled. Filters remove solid contaminant particles. N95 filters are lighter material and trap particles using an electrostatic media to grab particles. N99 and N100 filters are a heavier material and physically block the passage of particles through the media. Cartridges for chemical vapors and gases work by trapping vapors onto an absorbent media. These media are specific to the gas or vapor and are limited by the attraction between chemical and media, as well as the available surface area for adsorption.
For PAPR and SAR systems, air is provided into the facepiece on a pressure demand basis. This means that when the worker breathes, a valve opens allowing the filtered air into the breathing area. This valve closes once the necessary positive pressure returns. The positive pressure is not great enough to activate the exhalation valve, but provides enough extra push to eliminate the CO2 rebreathing issues found in full facepiece negative pressure APRs.
APRs work by filtering particles from the air or chemically purifying the air. APRs and filters are independently certified by the National Personal Protective Technology Laboratory (NPPTL) at NIOSH. These results have been verified independently in multiple peer reviewed journal articles, and the U.S. Army Research, Development, and Engineering Command. N95 and P100 filters are certified to remove 95% and 99.97%, respectively, of 0.3 µm (300 nm) particles. The Army nanoparticle research has shown effectiveness at sizes down to 50 nm. This is significant for construction applications because it shows that proper use of respirators can significantly reduce exposure to airborne particles of any size on a job site.
Effects on Productivity:
Respirator use has been found to impede physical effort, especially fine motor skills, and can impair cognitive functions.
PAPRs and SARs equipped with a helmet or hood can also perform with an APF of 1000. However, according to OSHA’s respiratory protection guideline, the employer must prove that APF 1000 level of protection is present. This is demonstrated through a WPF or SWPF (workplace protection factor or simulated workplace protection factor) study or equivalent testing. A WPF study uses data from respirators worn during work activities to provide APF data, while an SWPF study uses a laboratory setting.
Marc Scimonelli and Michael R. Cooper - Aria Environmental, Inc.
Bruce Lippy, PhD CIH - CPWR - The Center for Construction Research and Training
Sokas Rosemary, MD MOH- Georgetown University
- Sheet Metal & HVAC
- Weld, braze and solder seams and joints
W.W. Grainger, Inc.
To obtain information, visit MSA PAPR or contact 1-800-472-4643