Compressed air is the most common utility used in a typical industrial facility. It encompasses most operating aspects of the plant. The compressed air system can end up being the most expensive utility due to the focus that if production is running - then leave the system alone. Processes and machines are added and as long as the compressor can handle the increasing load - all is good. This brings us to our subject matter. The plant adds a process, a specialty coating line, requiring respirator protection. The plant determines supplied air respirators are the best choice. They want to be responsible and do the right thing so they start by reviewing what OSHA has to say on the subject.
This article is the report that could have been produced by the plant/facilities engineer, safety engineer and/or industrial hygienist. One of the least understood uses of compressed air is for breathing air. This report will cover the OSHA requirements for Grade D breathing air.
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Supplied Air Respirators Explained
Supplied air respirators (SAR) are used to reduce exposure to airborne contaminants present in many industries. Automotive assembly plant paint shops use respirators to control exposure to specialty coatings. Refineries and steel mills use SAR for confined space entry. Mobile sandblasting operations use SAR for worker comfort and protection. The applications are many and cross over almost all manufacturing sectors.
Supplied air respirators are defined as an atmosphere-supplying respirator that supplies the respirator user with breathing air from a source independent of the ambient atmosphere¹. Compressed air is commonly used as a source of air for SAR. This source can be low pressure, medium pressure or high pressure. We will limit our discussion to a medium pressure (75-125 PSIG) source from an air compressor.
What OSHA Says
The Occupational Safety and Health Administration (OSHA) regulates the quality of compressed air used for SAR under OSHA 1910.134 Subpart (i)².
The obvious objective of the standard is to provide a safe environment for the worker. Most users spend their efforts on the above chart but miss the other requirements within the standard. We will spend our remaining time on some of the more important issues.
Air Compressor Intake Concerns
Subpart (i) of OSHA 1910.134 states that “the employer shall ensure that compressors used to supply breathing to respirators are constructed and situated so as to prevent entry of contaminated air into the air-supplying system”. This has everything to do with the air compressor intake location. The compressors in a large industrial facility are often located in a dedicated room or separate building nowhere near the actual SAR use. The safety engineer normally concentrates on the hazard and the facility engineer concentrates on getting the compressed air to the needed area. Typically, no one looks at the compressor intake location. You do not want the intake(s) near the ground where truck/vehicle exhaust has a high concentration. Intakes located on the roof should be checked for proximity to process exhaust stacks.
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Sorbent Beds and Filtration
Next on the list is suitable in-line compressed air purifying sorbent beds and filters. Here it becomes more open to interpretation. We will dive head first into the technologies for compressed air filtration/purification that are commercially available in a future article. For now, let’s review some basics on what this part can mean.
Compressed air by nature becomes saturated during the compression process. Any drop in the compressor discharge temperature causes condensation to occur in the pipe. The dew point must be at least 10 F below the lowest ambient temperature to avoid condensation formation in the respirator. Remember to survey the entire piping system to determine if any piping is outside where temperatures are the lowest. Ice can actually form on some types of respirators (flooded hoods) if the compressed air is not properly dried. This subpart of the OSHA Standard allows some flexibility in selecting what is most appropriate for conditions in a specific workplace.
High Temperature and CO Monitors
There are two generic types of air compressors that OSHA covers; oil-lubricated and oil-free compressors. Carbon monoxide (CO) can be the most harmful contaminant produced by an oil-lubricated compressor. Compressor fires produce lethal amounts of CO instantaneously. A compressor fire can occur from any number of equipment failures. They are rare but do occur. One case occurred when the compressor was started with no cooling water, causing an explosion from the superheated air and oil. The compressor had no high temperature cut-off and did not monitor water flow.
OSHA requires oil-lubricated compressors to have a high temperature and/or CO monitor. If only a high temperature alarm is used, the supply air must be tested at intervals sufficient to prevent CO in the breathing air from exceeding 10 PPM. However, no one can predict when a catastrophic event, like a compressor fire or any high CO event will occur, making periodic CO testing meaningless.
In the same light, no one can predict when or if a rare high CO event will occur at the intake of an oil-free compressor. The practical response to this portion, of the OSHA Standard, is to install a CO monitor on any compressed air system used for breathing air. Typically the CO monitor is installed near the worker(s) wearing the respirator(s). Most CO monitors will have an audible alarm set to trigger at the 10 PPM level. This audible alarm may or may not be adequate protection. The user must be able to hear the alarm while the respirator is in use. A remote alarm may be required for confined space and paint booths where the user is separated from the CO monitor by a wall.
CO monitor panel with oil and odor removal filters
NIOSH Approval for SAR’s
Respirators need to be approved by the National Institute of Occupational Safety and Health (NIOSH). NIOSH uses an extensive test protocol to test respirators. The respirator and related items gain a Test Certification Number (TC#) upon approval. Most respirator manufacturers will require that Grade D or better air be supplied to their respirators.
One of the most important items that most facilities are clueless about is incompatible disconnects. The respirator manufacturer will generally offer several different disconnect coupling manufacturers. The employer must ensure that the respirator user cannot connect to the standard plant air system or worse yet, to an asphyxiate such as nitrogen or oxygen.
Supplied air respirator disconnect manifold meeting NIOSH requirements
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Compressed Air Testing
The frequency of compressed air quality testing is not specified. It is recommended to test on a regular basis for liability reasons. There are many third party testing labs dedicated to compressed air testing and even specializing in breathing air standards. Remember, testing only gives a sample at one point in time. Nothing will ensure worker safety more than a properly designed system from start to finish.
All maintenance items must be documented and stored in a designated area. OSHA 1910.134 also deals with respiratory selection, fit test program, maintenance, etc. - topics outside the scope of this article.
The idea here is that a properly designed compressed air SAR system requires an integrated effort including multiple engineering/plant disciplines. Everyone from the powerhouse, plant engineering and safety must come together in the planning stages. The end result everyone wants is to protect the worker, from the hazard, with equipment meeting OSHA requirements in a properly designed system.
¹ OSHA 1910.134 Subpart (b)
² OSHA 1910 .134 Subpart (i)
³ CGA 7.1 Table 1
⁴ OSHA 1910.134 Subpart(i)(5)(iii)
⁵ OSHA 1910.134 Subpart(i)(7)
⁶ NFPA CO Fact Sheet
To read similar articles on Compressed Air Standards, visit www.airbestpractices.com/standards.