Quick Jump Links
Respirator UseRespiratory Protection Program
Assigned Protection Factors & Respirator SelectionRespirators for Other Operations

Respirator Use

According to the OSHA website on Respiratory Protection, "Respirators have their limitations and are not a substitute for effective engineering and work practices controls", which are discussed in more detail in the Controls section.  "When it is not possible to use these controls to reduce airborne contaminants below their occupational exposure levels, such as during certain maintenance and repair operations, emergencies, or when engineering controls are being installed, respirator use may be the best or only way to reduce worker exposure.  In other cases, where work practices and engineering controls alone cannot reduce exposure levels to below the occupational exposure level, respirator use is essential." 

The Silica Standards specify that respiratory protection is required:
  • Where specified in Table 1 of the Construction Standard (29 CFR.1926.1153);

  • Where exposures exceed the PEL during periods necessary to install or implement feasible engineering and work practice controls;

  • Where exposures exceed the PEL during tasks, such as certain maintenance and repair tasks, for which engineering and work practice controls are not feasible;

  • During tasks for which an employer has implemented all feasible engineering and work practice controls and such controls are not sufficient to reduce exposures to or below the PEL; and,

  • During periods when the employee is in a regulated area (General Industry and Maritime).

Respiratory Protection Program

When respirators are used to control employee exposure to crystalline silica, a comprehensive respiratory protection program must be developed. Respirators are only effective when properly selected, fitted, and maintained.

A respiratory protection program should meet the requirements of the OSHA standard for Respiratory Protection (29 CFR 1910.134) and ANSI Standard Z88.2-1992 (American National Standard for Respiratory Protection). According to these standards, Important elements of a respiratory protection program include:

  • A written respiratory protection program with worksite-specific procedures and elements for required respirator use.

  • Periodic personal air sampling of the exposed employees.

  • Proper selection of respirators based on the process and exposure concentrations.

  • A training program, repeated annually, for all employees who use respirators to control their exposure to airborne contaminants (silica dust).

  • A medical evaluation of the worker's ability to perform the work while wearing a respirator.

  • Initial and annual respirator fit testing, and training in performing "user seal checks" (positive and negative pressure fit checks).

  • Respirator maintenance, inspection, cleaning and storage procedures.

  • Procedures to evaluate the effectiveness of the respiratory protection program.

If employees voluntarily wear respirators, employers must still establish and implement certain program elements to address voluntary respirator use.

The sample Respirator Assignment and Training Record can be used to document (1) which respirators are assigned to which employees and, (2) the completion of the relevant respirator training requirements.


Assigned Protection Factors and Respirator Selection

The ability of any respirator to reduce a given exposure to silica depends primarily upon the design of the respirator. Different respirators offer different levels of protection, and those differences must be taken into account when selecting a respirator. ANSI, NIOSH and OSHA, in their respirator standards and guidelines, list Assigned Protection Factors (APF) for different respirator types. These APFs are used to help select respirators that offer sufficient protection against the exposure.

The OSHA respirator standard 29 CFR 1910.134 defines the Assigned Protection Factors (APF) as "the workplace level of respiratory protection that a respirator or class of respirators is expected to provide to employees when the employer implements a continuing, effective, respiratory protection program."  When selecting a respirator, the ratio of an employee's silica exposure to the OSHA PEL/ACGIH TLV determines the minimum APF a respirator must provide.

To determine the Assigned Protection Factor needed for a given silica exposure, the following formula, per NIOSH Respirator Selection Logic - 2004, is used:

Hazard Ratio =
Employee Silica Exposure (mg/m3)

A respirator should be selected with an Assigned Protection Factor greater than the Hazard Ratio.

For example, if an employee's 8-hour silica exposure is 0.4 milligrams per cubic meter of air (mg/m3), and the OSHA PEL is 0.05 mg/m3, the Hazard Ratio is 8. As shown in Table R-1, a quarter mask respirator has an APF of 5, while a Half-Mask respirator has an APF of 10.  Since the Hazard Ratio (8) is higher than 5, the Half-Mask respirator is selected.

OSHA recognizes that many of its PELs are outdated and inadequate for ensuring protection of worker health.  To better protect workers, OSHA has annotated the existing Z-Tables with other selected occupational exposure limits, such as the ACGIH TLVs.  OSHA recommends that employers consider using the alternative occupational exposure limits because the Agency believes that exposures above some of these alternative occupational exposure limits may be hazardous to workers, even when the exposure levels are in compliance with the relevant PELs.

Therefore, it is suggested that respirators be worn when employee silica exposures exceed the ACGIH TLV and OSHA Action Level of 0.025 mg/m3.  In the above example, the employee's 8-hour silica exposure of 0.4 mg/mis 16 times the TLV and Action Level.  As shown in Table R-1, the Half-mask respirator has an APF of 10, which is below the Hazard Ratio of 16. Therefore a respirator should be selected with an APF of 25 or greater.   

The following table, taken from the OSHA Respiratory Protection Standard 29 CFR 1910.134, provides assigned protection factors for various respirator types.


Table R-1: Assigned Protection Factors (5)
Type of Respirator (1, 2)Quarter MaskHalf MaskFull FacepieceHelmet/HoodLoose-fitting
1. Air-purifying Respirator5(3) 1050------
2. Powered Air-Purifying Respirator (PAPR)----501000(4) 25/100025
3. Supplied-Air Respirator (SAR) or Airline Respirator -
  • Demand Mode
  • Continuous flow mode
  • Pressure-demand or other positive pressure mode




(4) 25/1,000

4. Self-Contained Breathing Apparatus (SCBA)
  • Demand Mode
  • Positive-pressure demand or other positive-pressure mode
(e.g., open/closed circuit)

*Respirator has APF of 50 only with quantitative fit testing.

(1) Employers may select respirators assigned for use in higher workplace concentrations of a hazardous substance for use at lower concentrations of that substance, or when required respirator use in independent of concentration.

(2) The assigned protection factors in Table 1 are only effective when the employer implements a continuing, effective respirator program as required by this section (29 CFR 1910.134), including training, fit testing, maintenance, and use requirements.

(3) This APF category includes filtering facepieces and half masks with elastomeric facepieces.

(4) The employer must have evidence provided by the respirator manufacturer that testing of these respirators demonstrates performance at a level of protection of 1,000 or greater to receive an APF of 1,000.  This level of performance can best be demonstrated by performing a WPF or SWPF study or equivalent testing.  Absent such testing, all other PAPRs and SARs with helmets/hoods are to be treated as loose-fitting facepiece respirators, and receive an APF of 25.

(5) These APFs do not apply to respirators used solely for escape.  For escape respirators used in association with specific substances covered by 29 CFR 1910 Subpart Z, employers must refer to the appropriate substance-specific standards in that subpart.  Escape respirators for other IDLH atmospheres are specified by 29 CFR 1910.134 (d)(2)(ii).

Abrasive Blasting

OSHA standards (29 CFR 1910.94 and 29 CFR 1926.57), pertaining to abrasive blasting, specify the use of abrasive blasting respirators.  An abrasive blasting respirator is constructed so that it covers the wearer's head, neck, and shoulders to protect them from rebounding abrasive.  Abrasive blasting respirators must be worn:

  • Where abrasive blasting is conducted using crystalline silica containing blasting agents, or

  • Where abrasive blasting is conducted on substrates that contain crystalline silica, or

  • When working inside of blast cleaning rooms, or

  • When using silica sand in manual blasting operations where the nozzle and blast are not physically separated from the operator in an exhaust ventilated enclosure, or

  • Where concentrations of toxic dust dispersed by the abrasive blasting may exceed the limits set in 1910,1000 and /or 1926.55 and the nozzle and blast are not physically separated from the operator in an exhaust-ventilated enclosure.
Properly fitted particulate filter respirators, commonly referred to as dust-filter respirators, may be used for short, intermittent, or occasional dust exposures such as cleanup, dumping of dust collectors, or unloading shipments of sand at a receiving point, when it is not feasible to control the dust by enclosure, exhaust ventilation, or other means. The respirators used must be approved by NIOSH under 42 CFR part 84 for protection against the specific type of dust encountered.

NIOSH-certified, Type CE abrasive-blasting respirators are the only respirators suitable for use in abrasive-blasting operations. Currently, four Type CE abrasive-blasting respirators are certified by NIOSH:

  • A continuous-flow respirator with a loose-fitting hood and an assigned protection factor (APF) of 25.

  • A continuous-flow respirator with a tight-fitting facepiece and an APF of 50.

  • A positive-pressure respirator with a tight-fitting half-mask facepiece and an APR of 1,000.

  • A pressure-demand or positive-pressure respirator with a tight-fitting facepiece and an APF of 2,000.

For abrasive blasting using crystalline silica, NIOSH recommends that workers wear a Type CE, pressure-demand or positive-pressure, abrasive-blasting respirator (APF of 1,000 or higher). These protection factors are often needed because of the high silica exposures during sandblasting.


Respirators for Other Operations

For operations other than abrasive blasting with crystalline silica, Table R1 lists the minimum respiratory protection equipment required to meet the OSHA PEL for crystalline silica under given exposure concentrations. The most protective respirator should be selected consistent with the tasks to be performed.  Note:  The OSHA Construction Silica Standard (29 CFR 1926.1053) specifies minimum respiratory protection for specific operations in Table 1.

The following sample forms can be used to document respirator selection and employee assignment of respirators.
Sample Employee Respirator Assignment and Training Record


 2017  The Zurich Services Corporation.   All rights reserved.