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Any employer who requires or permits employees to wear a respirator must have a written respiratory protection program. This is required by OSHA in both of their asbestos standards and their respiratory protection standard (29 CFR 1910.134). The written respirator program establishes standard operating procedures concerning the use and maintenance of respiratory equipment. In addition to having such a written program, the employer must also be able to demonstrate that the program is enforced and updated as necessary.
|CPL 02-00-120 - CPL 2-0.120 -
Inspection procedures for the Respiratory Protection Standard.
|• Record Type:||Instruction|
|• Directive Number:||CPL 02-00-120|
|• Old Directive Number:||CPL 2-0.120|
|• Title:||Inspection procedures for the Respiratory Protection Standard.|
|• Information Date:||09/25/1998|
|• Standard Number:||1910.134|
[This document was edited on 7/14/2004 to strike information that no longer reflects current OSHA policy. On 12/31/2003, 29 CFR 1910.139 was revoked and the 1997 proposed standard on Occupational Exposure to Tuberculosis (TB) was withdrawn in the Federal Register. The changes to this directive were approved by the Assistant Secretary John Henshaw on 7/13/2004. The added language is marked by an asterisk (*) at the beginning and the end of the paragraph.]
By and Under the Authority of
TABLE OF CONTENTS
CHANGE SCHEDULES GUIDE - A LISTING OF METHODS
The program must be tailored to cover the specific work operations and practices in the workplace. The provisions listed in paragraph (c)(1)(i) thru (ix) of the standard must be included in the written program unless it is determined they are not applicable.
These provisions are to be considered when evaluating a written program:
Compliance with the program should be verified during the walkaround by personal observation and employee interviews.
Use of elastomeric or supplied-air respirators, even when voluntary on the part of the employee, will require the employer to include all elements in a written program that will ensure use of these respirators does not create a hazard.
Companies with multiple worksites may have a program administrator at each worksite, as long as this person is qualified and retains the accountability and responsibility for the day-to-day operation of the specific program for that site. Alternatively, a company may opt to have one program administrator for several sites and/or one program for several similar sites as long as the program contains the necessary elements and addresses the hazards at those sites.
In regards to mathematical predictive equations, their
use should be limited to situations where workplace factors,
such as contaminant release and ventilation system
performance, are fairly constant over the work shift and
predictable. The results should incorporate reasonable
safety factors and be interpreted conservatively. CSHO's
must exercise a great deal of professional judgement in
concluding if the mathematical approach provides appropriate
guidance. (e.g., The methylene chloride standard forbids the
use of APR's for protection against methylene chloride and
would supercede any model which predicts a changeout time
for this chemical.) The CSHO should examine the employer's Hazard
Communication Program for further information on existing
respiratory hazards in the workplace. The Hazard Communication Standard requires employers to
inventory the hazardous chemicals in their workplace and to
maintain copies of material safety data sheets (MSDS) for
each hazardous chemical. In a similar manner under the
respirator standard, the employer must examine the workplace
and determine if the quantity, circumstances, and use of the
hazardous chemicals require further evaluation for
respiratory hazards. MSDSs contain information such as
physical and chemical characteristics and hazards, primary
route(s) of entry, and generally applicable control
measures. Some MSDSs include some recommendations on
appropriate respiratory protection. For those chemicals that do present a potential
respiratory hazard, employers can contact the chemical
manufacturer for additional information on predicted
exposure levels and methods to further control worker
exposure. The CSHO should be aware of the potential for an
emergency situation and the type of respirators selected.
The employer must provide the appropriate emergency escape
respirator in the immediate work area for employee use and
address emergency use respirators in the written respirator
program. The CSHO should also investigate, through routine
employee interviews, what actions the employer has taken to
re-evaluate employee exposure when employees have made
health complaints to determine if appropriate action has
been taken to address a respiratory hazard. Respirators required to be used in the workplace must be
NIOSH-approved and appropriate for the hazard. Part 84
respirators with an "N" designation should not be used in
work settings where oil aerosols are generated, while those
with an "R" designation should be used for only one shift
when oil is present. Respirators with a "P" designation may
be used for more than one work shift, even when oil is
present. Employers must follow respirator manufacturer's
recommendations. Inappropriate respirators [(d)(1)(i)] should be cited
when the CSHO documents an overexposure is possible, and a
suitable respirator is not being used for protection against
that exposure . Unapproved [(d)(1)(ii)] respirators can be
cited even where an overexposure has not been established.
Use of objective data - this is the use of data obtained
from industry studies, trade associations, or from tests
conducted by chemical manufacturers which demonstrate that
air contaminants cannot be released in the workplace in
airborne concentrations that are IDLH. The objective data
shall represent the highest contaminant exposures likely to
occur under reasonably foreseeable conditions of processing,
use, or handling. The employer must document the use of
objective data as part of their written program.
Application of mathematical approaches - the preamble to
the final rule (p. 1199) states that employers can use data
on the physical and chemical properties of air contaminants,
combined with information on room dimensions, air exchange
rates, contaminant release rates, and other pertinent data
including exposure patterns and work practices to estimate
the maximum exposure that could be anticipated in the
As a continuing practice, employers are required to
identify hazards as a result of changes in the workplace
such as a change in equipment, process, products, or control
measures that could result in new exposures. Appropriate
respirators should be provided as necessary.
end-of-service life or end of shift
(whichever occurs first)
end-of-service life or beginning of
shift (whichever occurs first)
every 1, 2 or 4 hours dependent on
concentration according to Table 1 and at beginning
of each shift
for cartridges every three hours or
end of shift (whichever is sooner); for canisters,
every 2 or 4 hours according to the schedule in
end-of-service life or end of shift
in which they are first used (whichever occurs
Methylene chloride -
canisters may only be used for
emergency escape and must be replaced after use.
In regards to mathematical predictive equations, their use should be limited to situations where workplace factors, such as contaminant release and ventilation system performance, are fairly constant over the work shift and predictable. The results should incorporate reasonable safety factors and be interpreted conservatively. CSHO's must exercise a great deal of professional judgement in concluding if the mathematical approach provides appropriate guidance. (e.g., The methylene chloride standard forbids the use of APR's for protection against methylene chloride and would supercede any model which predicts a changeout time for this chemical.)
The CSHO should examine the employer's Hazard Communication Program for further information on existing respiratory hazards in the workplace.
The Hazard Communication Standard requires employers to inventory the hazardous chemicals in their workplace and to maintain copies of material safety data sheets (MSDS) for each hazardous chemical. In a similar manner under the respirator standard, the employer must examine the workplace and determine if the quantity, circumstances, and use of the hazardous chemicals require further evaluation for respiratory hazards. MSDSs contain information such as physical and chemical characteristics and hazards, primary route(s) of entry, and generally applicable control measures. Some MSDSs include some recommendations on appropriate respiratory protection.
For those chemicals that do present a potential respiratory hazard, employers can contact the chemical manufacturer for additional information on predicted exposure levels and methods to further control worker exposure.
The CSHO should be aware of the potential for an emergency situation and the type of respirators selected. The employer must provide the appropriate emergency escape respirator in the immediate work area for employee use and address emergency use respirators in the written respirator program.
The CSHO should also investigate, through routine employee interviews, what actions the employer has taken to re-evaluate employee exposure when employees have made health complaints to determine if appropriate action has been taken to address a respiratory hazard.
Respirators required to be used in the workplace must be NIOSH-approved and appropriate for the hazard. Part 84 respirators with an "N" designation should not be used in work settings where oil aerosols are generated, while those with an "R" designation should be used for only one shift when oil is present. Respirators with a "P" designation may be used for more than one work shift, even when oil is present. Employers must follow respirator manufacturer's recommendations.
Inappropriate respirators [(d)(1)(i)] should be cited when the CSHO documents an overexposure is possible, and a suitable respirator is not being used for protection against that exposure . Unapproved [(d)(1)(ii)] respirators can be cited even where an overexposure has not been established.
Change schedules for all other gases and vapors must be established and implemented by the employer. OSHA has stated in the preamble to the final rule that the employer is not required to research and analyze experimental breakthrough data, but may obtain information from sources who have expertise and knowledge that can help the employer to develop reasonable change schedules. The new standard prohibits the use of warning properties as the sole basis for determining change schedules. However respirator users should be trained to understand that abnormal odor or irritation is evidence that respirator cartridges need to be replaced. Where an effective change schedule is implemented, air-purifying gas and vapor respirators may be used for hazardous chemicals, including those with few or no warning properties.
The change schedule for a mixture should be based on reasonable assumptions that include a margin of safety for the worker wearing the respirator. Where the individual compounds in the mixture have similar breakthrough times (i.e. within one order of magnitude), service life of the cartridge should be established assuming the mixture stream behaves as a pure system of the most rapidly migrating component or compound with the shortest breakthrough time (i.e., sum up the concentration of the components). Where the individual compounds in the mixture vary by 2 orders of magnitude or greater, the service life may be based on the contaminant with the shortest breakthrough time. OSHA believes that an approach such as this reflects good health and safety practice where neither objective or experimental data is available for the mixture.
OSHA believes that change schedule information will become more available to the respirator user community and will evolve in quality. The CSHO should review the written respiratory protection program to ensure that it describes the information and data relied upon and the basis for the canister and cartridge change schedule and the basis for reliance on the data as required by the standard. Again, CSHOs should exercise judgement in evaluating mathematical models, rules of thumb, experimental data, use of analogous chemical structures, and other reasoned approaches.
Where employers use a transient workforce, (e.g., temporary or construction workers), the employer may accept the written medical recommendation of the employee's ability to use a respirator as determined by their previous employer's PLCHP only if the work conditions and type and weight of the respirator remains the same and appropriate for use at their new work site. In this situation, the employer must obtain from the previous employer a copy of the PLCHPs written recommendation.
Section (e)(2)(ii) requires the employer to obtain the information required in the questionnaire or provide the initial examination prior to performing fit testing of employees and prior to requiring the employee to wear the respirator in the workplace. When using the questionnaire, the employer may not change the wording of questions in Part A , if the form is being used as the sole means to evaluate employees. The Physician or other Licensed Health Care Professional (PLHCP) may add questions to the questionnaire that could assist in determining whether the employee can perform the work while wearing respiratory protection.
In order to maintain strict confidentiality of the information obtained in the questionnaire, the employer's role is limited to distributing the blank questionnaire to the employee for him or her to fill out, or providing it to the PLHCP, who will administer the questionnaire to the employee. If the employer provides the questionnaire to the employee, an addressed and postage-paid envelope should also be provided for the employee to mail it to the PLHCP. The questionnaire and findings may also be maintained by the employer's medical office, if the health office is administratively separate from the employer's central administration offices.
If the employer does not have or chooses not to use an in-house medical staff, arrangements must be made for a physician or other licensed healthcare professional (PLHCP) to perform the medical evaluations. The PLHCP may be a physician, a registered nurse, a nurse practitioner, a physician assistant, or other licensed health care professional acting within the scope of his or her state license, registration, or certification. The PLCHP must be legally permitted by his or her professional license to conduct the type of medical evaluation required by the respirator standard. Scope of practice for non-physician PLCHPs will vary from state to state. All PLCHPs who participate in any aspect of the medical evaluation must be practicing within the scope of their license. For assistance in determining which state licensing board or agency to contact to determine a PLCHP's legally permitted scope of practice, the CSHO can contact the Directorate of Technical Support in OSHA's National Office.
The employer must ensure that the questionnaire is administered in such a manner that employees can understand the content and the confidentiality of the record is maintained. Where the employee cannot understand English, the employer must have the questionnaire translated into the employee's language either through a translator or a translated written copy. The questionnaire has been translated into Spanish and is available on OSHA's homepage (www.osha.gov) in the Respirator Q & A Document. In cases where the employee cannot read, the employee can request someone other than the employer to orally read them the questionnaire or the PLHCP may obtain through an interview or examination the same information requested on the medical questionnaire.
The CSHO should determine what supplemental information was given to the PLHCP by the employer. This can be done through interviewing the PLHCP or reviewing documentation from the employer. If the employer is relying on a medical evaluation for the employee from a previous employer (which is allowed only when the employer uses a transient workforce), the CSHO should determine that the work conditions and respirator remained the same.
If the CSHO suspects the employee(s) did not receive a medical evaluation or have not answered the questionnaire honestly (e.g., been "coached" by the employer on how to respond to the mandatory questions from Appendix C), then the CSHO should ask to interview the PLHCP. If this interview still results in questions, the CSHO may wish to obtain a Medical Access Order and review the actual medical questionnaire and/or the physical examination records where necessitated by this paragraph of the rule.
The CSHO should also ensure that any required physical examinations have in fact been conducted, as per (e)(3) and (e)(7). A positive answer to any question in Part A, Section 2, Questions 1-8 (also questions 10-15 for SCBA and full-face respirator users) requires a follow-up by the PLCHP. The PLCHP may evaluate positive responses through consultation with the employee to determine if the positive response is not relevant to the employee's ability to wear a respirator or if further physical examination is necessary (e.g., brief smoking history in the past, as compared to current heavy smoker status).
If questions arise regarding the issue of qualifications of the PLHCP, the CSHO should inquire with the state licensing board or the applicable registration or certification agencies in that state to ensure that the PLCHP is acting within the scope of his or her practice.
The fit test must be performed before the respirator is used in the workplace. It must be repeated at least annually and whenever a different respirator facepiece is used or a change in the employee's physical condition could affect respirator fit. If the respirator subsequently becomes unacceptable (i.e., causes irritation or pain to the employee) to the employee, the employee must be given the opportunity to select a different respirator facepiece and be retested.
Qualitative Fit-Testing (QLFT) may be used to fit test negative pressure air-purifying respirators, if they will only be used in atmospheres less than ten times the PEL, since existing evidence only validates the QLFT protocols listed in Appendix A to identify respirators that achieve a fit factor of 100. For greater concentrations, Quantitative Fit-Testing (QNFT) must be used. When quantitative fit-testing is used, all full-facepiece respirators must meet or exceed a fit factor of 500, while quarter - and half-mask respirators must meet or exceed 100. For all positive pressure, atmosphere-supplying respirators, either qualitative or quantitative fit testing may be used. While atmosphere-supplying respirators are fit-tested in the negative pressure mode, these respirators are most often used as positive pressure respirators in the workplace. Positive pressure atmosphere-supplying respirators that pass the QLFT or QNFT fit test may be used at the higher protection factors assigned these respirators. See Table 1 for a summary.
Acceptable Fit-Testing Methods
|Half-Face, Negative Pressure, APR (<100 fit factor)||Yes||Yes|
|Full-Face, Negative Pressure, APR (<100 fit factor) used in atmospheres up to 10 times the PEL||Yes||Yes|
|Full-Face, Negative Pressure, APR (>100 fit factor)||No||Yes|
|Supplied-Air Respirators (SAR), or SCBA used in Negative Pressure (Demand Mode) (>100 fit factor)||No||Yes|
|Supplied-Air Respirators (SAR), or SCBA used in Positive Pressure (Pressure Demand Mode)||Yes||Yes|
|SCBA - Structural Fire Fighting, Positive Pressure||Yes||Yes|
|SCBA/SAR - IDLH, Positive Pressure||Yes||Yes|
|Mouthbit Respirators||Fit-testing Not Required|
|Loose-fitting Respirators (e.g., hoods, helmets)|
Employees should be observed to determine if the seal check procedures are being performed each time the respirator is donned. The procedure used must be one listed in Appendix B-1 or recommended by the manufacturer if the employer demonstrates it is as effective as those listed in Appendix B-1. Alternative seal checks must be based on scientific studies. [The face fit is considered satisfactory if a slight positive pressure can be built up inside the facepiece when the exhalation valve or surface is covered, the user exhales gently, and there is no evidence of outward leakage at the seal. The negative check requires covering the inlet opening or surface, inhaling gently, and having the facepiece remain in a slightly collapsed condition with no inward leakage of air detected.]
Section (g)(2)(ii) requires that employers ensure that employees leave the respirator-use area to correct certain problems associated with respirator use, including the detection of contaminant breakthrough, and to replace the respirator or its filters or cartridges. Employees should be interviewed [e.g., What do you do if you notice a leak? ] to determine whether there are any policies or actions which would prohibit or impede them from leaving the area should they have significant problems with their respirators or which impede the replacing of filters or cartridges. Paragraph (g)(2)(iii) is designed to prevent employees from reentering a workplace after leaving because of a significant respirator failure without first assuring the proper functioning of the respirator.
For work performed outside of visual contact, voice, radio or signal line are permitted. CSHOs should specifically review protocols for communication, rescue, and notification for employees entering IDLH atmospheres. Communication protocols must be established that allow the standby person to monitor entrant status and enable the standby(s) to alert entrants of the need to evacuate the area. It is not sufficient to rely on the employees in the IDLH area to call for help when needed.
Paragraph (g)(3) does not apply to IDLH atmospheres in a permit-required confined space (PRCS) or to environments in which there is an uncontrolled release of a hazardous substance. IDLH atmospheres in a PRCS are specifically addressed in the PRCS standard, 1910.146, and its accompanying directive, CPL 2.100. Environments in which there is an emergency release of a hazardous substance are addressed in paragraph (q) of OSHA's HAZWOPER standard, 1910.120 or 1926.65, and its accompanying directive, CPL 2-2.59A. In facilities where an uncontrolled release of a hazardous substance could create an emergency IDLH atmosphere, employers must follow the requirements of HAZWOPER paragraph (q). These situations must be addressed in the employer's emergency response plan and the response procedures must be consistent with that standard.
The provision is limited to workers performing an interior attack on an interior structural fire. In Subpart L ( 1910.155), OSHA has defined "interior structural fire fighting" to mean: "the physical activity of fire suppression, rescue or both, inside of buildings or enclosed structures which are beyond the incipient stage." This is firefighting to control or extinguish a fire in an advanced stage of burning, producing large amounts of smoke, heat and toxic products of combustion. Firefighter exposure during this activity is extremely hazardous. The atmosphere is considered IDLH and the use of Self Contained Breathing Apparatus is required. By contrast, incipient stage fire fighting involves the control or extinguishment of a fire in the initial or beginning stage, using portable fire extinguishers or small hose lines without the need for personal protective equipment. It is the incident commander's responsibility, based on training and experience, to judge whether a fire is an interior structural fire, and how it will be attacked.
OSHA has discussed this provision in a number of documents.
There must always be at least two firefighters
stationed outside during interior structural
firefighting, and they must be trained, equipped and
prepared to enter if necessary to rescue the
firefighters inside. However, the incident commander
has the responsibility and flexibility to determine
when more than two outside firefighters are
necessary given the circumstances of the fire. The
two-in/two-out rule does not require an arithmetic
progression for every firefighter inside, i.e. the
rule should not be interpreted as 4-in-4-out,
It is important that the CSHO recognize that
life-saving activities in interior structural fire
fighting are not precluded by the standard. There is
an explicit exemption in the standard that if life
is in jeopardy, firefighters have the discretion to
perform the rescue, and the "two-in/two-out"
requirement is waived. There is no violation of the
standard under such life-saving rescue
The two-in/two-out provision is not intended as
a staffing requirement. It does not require fire
departments to hire additional firefighters; it does
not require four-person fire companies; it does not
require four persons on a fire truck. Most fire
departments have more than four firefighters and can
assemble the numbers required on the scene by
waiting for others to arrive. During this time the
fire may be attacked only from the outside,
sizing-up operations may occur, and emergency rescue
necessary to save lives may take place as discussed
above. The "two-in/two-out" rule is a worker safety
practice requirement, not a staffing requirement.
The standard allows one of the standby
firefighters to have other duties such as serving as
the incident commander, safety officer, or operator
of fire apparatus. However, one of the outside
firefighters must actively monitor the status of the
inside firefighters and may not be assigned
additional duties. The second outside firefighter
may be involved in a wide variety of activities.
Both of the outside personnel must be able to
provide support and assistance to the two interior
firefighters; any assignment of additional duties
for one of the outside firefighters must be weighed
against the potential for interference with this
requirement. Proper assignment of firefighting
activities at an interior structural fire must be
determined on a case-by-case basis and is dependent
on the existing firefighting situation. Compliance
will always depend on consideration of all the
worksite variables and conditions, and the judgement
of the incident commander is critical in meeting
this performance standard.
The two firefighters (buddies) entering an IDLH
atmosphere to perform interior structural
firefighting must maintain visual or voice
communication at all times. Electronic methods of
communication such as the use of radios shall not be
substituted for direct visual contact between the
team members in the danger area. However, reliable
electronic communication devices are not prohibited
and certainly have value in augmenting communication
and may be used to communicate between inside team
members and outside standby personnel.
For further explanation refer to the preamble of
the Respiratory Protection standard (vol. 63, No. 5,
1245-1248) and the Respirator Question and Answer
document (August 3, 1998). Both documents can be
found at OSHA's Homepage -
The employer must ensure that respirators are inspected before each use and during cleaning. The CSHO should observe the condition of the respirators being used in the workplace. One or more respirators should be checked before employees enter, or as they leave the respirator area. A minimally acceptable inspection procedure for ALL respirators includes a check of respirator function, tightness of connections and the condition of the various parts, including but not limited to, the face piece, head straps, valves, connecting tube, and cartridges, canisters, or filters, and a check of the respirator's elastomer parts for pliability and signs of deterioration.
SCBA's also require an inspection of the air and oxygen cylinders to assure that the cylinder pressure is maintained at 90% of the manufacturer's recommended pressure level and that the regulator and low pressure warning devices function properly. To assure that both the regulator and low pressure warning devices function properly the warning device must be activated and heard by the person performing the inspection. The CSHO should interview the individual who is inspecting SCBA's to determine if these regulator and low pressure warning devices are being activated according to the respirator manufacturer's instructions.
The CSHO should also observe how respirators are stored in the workplace. Respirators must be properly stored to protect them against physical damage, contamination, excessive moisture, extreme temperatures, sunlight, and damaging chemicals. Emergency use respirators must be stored in compartments OR in covers, both of which must be clearly marked as containing the emergency respirators.
For air compressors that are not oil lubricated, a CO alarm is not required. However, the employer is required to ensure that carbon monoxide levels in the breathing air do not exceed 10 ppm. Some practical methods for ensuring that the carbon monoxide level does not exceed 10 ppm include; placing the air intake for the compressor in an area that the employer knows is free from contaminants; frequent or continuous monitoring of the breathing air supply; the use of carbon monoxide filters; or the use of a high temperature alarm or shut off devices.
If the employer is using an oil-lubricated air compressor, it must have either a carbon monoxide alarm, high temperature alarm, or both. If only a high temperature alarm is used, then the breathing air must be tested for the presence of carbon monoxide at intervals sufficient to ensure that carbon monoxide levels do not exceed 10 ppm. The alarm must be able to alert the users or another employee who knows to alert any respirator users.
If cylinders are used they must be marked with a NIOSH approval label. Cylinders of purchased breathing air must have a certificate of analysis from the supplier that the breathing air meets the required Grade D air and moisture content.
If compressed or liquid oxygen is used, it must meet the specifications for breathing oxygen outlined by the United States Pharmacopoeia (USP). Compressed oxygen must not be used for any respirators that previously used compressed air.
All breathing air couplings must be incompatible with those of non-respirable air or other gases used at the site to prevent inadvertent servicing of air line respirators with non-respirable gases or oxygen.
Employees should be interviewed to determine if they have received the required training and the extent of that training. If the CSHO detects a trend in employee responses that indicate training is not being conducted, or is conducted in a cursory manner, a closer review of the training program is necessary.
Employees who voluntarily wear respirators must, at least, be given the information in Appendix D.
Fit test records must be kept until the next fit test is administered. Each fit test record must contain the employee identification, type of fit test, date last tested, the results of the test, and the make, model and size of the respirator tested. The CSHO should review these records to verify that fit-testing is being done annually and confirm that the fit-tested respirators are the same models and sizes as those observed in the workplace.
The CSHO should also check on the availability of the written program.
Lack of a fit test record or lack of information on a fit test record would be cited under (m)(2). If an employee is wearing a respirator different from that found in his fit test records then (f)(2) should be cited. Improper fit testing procedures would similarly be cited under the appropriate subparagraph in (f).
Instructions for the use of respiratory protection by CSHO's are contained in OSHA Instruction CPL 2-2.54. The CSHO should closely review and examine all the data available on site concerning the exposures or potential exposures in this particular location. If the employer cannot supply adequate data to support the selection of the types of respirators that are in use, the CSHO must not enter the areas where respirators are in use. If the hazard determination performed by the employer has been completed in accordance with the standard, the CSHO must don the appropriate respirator required in that work-site prior to the walkaround in areas where respirators are required.
CHANGE SCHEDULES GUIDE - A LISTING OF METHODS
A brief description of some currently available approaches or methods for respirator cartridge change schedules is presented below. The CSHO should assess the "Good Faith" efforts of the employer on a case by case basis and contact appropriate regional OR National office staff for guidance, as necessary. This is not intended to be an exhaustive list, but a summary of some reasonable methods that an employer may take in creating a change schedule. No matter which method is used, the employer must maintain any data used in making their decision as part of their program.
Manufacturers Objective Data: Respirator cartridge model-specific objective data that is available from the manufacturer or through a distributor may be used to establish change schedules. Objective data may be presented in tabular or graphical format or simply provided verbally over a manufacturer's telephone help line. Some manufacturers have developed elaborate computer programs available on the Internet that provide the necessary objective data to the user.
Experimental Methods: Experimental breakthrough-time data from a laboratory based on worst case testing of simulated workplace conditions. This method can provide fairly accurate service life data compared to other available methods.
Mathematical Predictive Modeling: One tool that has demonstrated value is the use of mathematical modeling based on predictive equations. These models are typically complex and require considerable expertise to apply. They also require some proprietary information from the respirator manufacturer. OSHA fully supports the further development and validation of these models. The agency believes that respirator manufacturers may be in the best position to apply them to their products.
Analogous Chemical Structures: Employer would rely on service life values from other chemicals having analogous chemical structure to the contaminant under evaluation for breakthrough. Or in some cases a chemical with known migration may reasonably be anticipated to act as a surrogate for a similar chemical that would have less rapid migration (e.g., an employer could assume that a heavier, less volatile compound than another in the same chemical series that had been tested for breakthrough would breakthrough no faster than the latter compound, such as benzene versus toluene.) The use of this method requires a substantial amount of judgement and assumption of similar chemical properties. The use of analogous chemical structures should be infallible as long as objective data or information for lower molecular weight compounds is used to predict the breakthrough times for higher molecular weight analogues containing only additional methyl or phenyl groups. Data from higher molecular weight groups should not be used to predict the behavior of analogous substances with lower molecular weight. This approach relies heavily on experimental data and expert analysis. This method may be less accurate than others and should be used only when better information is not available.
Workplace Simulations: Unvalidated methods exist or are under development where the respirator cartridge is tested in the workplace in "real time" and under actual conditions of use. Simple designs have been informally described to the agency. Workplace air during representative conditions is drawn over the cartridge at a rate approximating normal breathing at a higher work rate. An air sampling/analytic device would be placed on the other side of the filter to measure the time of breakthrough. Employers could incorporate this type of testing into their air monitoring program using sampling strategies established in their workplace. In theory, these approaches should be an accurate method for determining change schedules and could accommodate fluctuating conditions of humidity, concentration, etc., to allow less conservative schedules that utilize a larger fraction of the true service life.
Rules of Thumb: Generalized rules or guidance can be generated from experimental work. Presented below is a rule of thumb for estimating organic vapor service life found in Chapter 36 of the American Industrial Hygiene Association publication
"The Occupational Environment Evaluation and Control".
*If a chemical's boiling point is >70 C and the concentration is
less than 200 ppm you can expect a service life of 8 hours at a
normal work rate.
Note: This first rule of thumb needs further review.
* Service life is inversely proportional to work rate.
* Reducing concentration by a factor of ten will increase service life by a factor of five.
* Humidity above 85% will reduce service life by 50%.
These generalizations should only be used in concert with one of the other methods of predicting service life for specific contaminants.
If you need help developing a respiratory protection program, call EHSO at 770-645-0788!