Low Pressure Breathing Air Preparation
I was asked recently to give a recommendation for a breathing air system and just like a lot of things I run into in industry there are a lot of factors that come into play with breathing air systems. Would you know what to specify or even what standards apply?
Here is some of the results of my high level research. First off I am going to be discussing low pressure breathing air preparation rather than the type you use in firefighting self-contained breathing apparatus (SCBA) or underwater scuba applications. For this blog I am going to narrow down the topic to low pressure breathing air for industrial uses, such as in an environment such as chemical manufacturing, abrasive blasting, paint spraying, industrial cleaning, or arc welding. In these type of operations the user desires to breathe clean air rather than the contaminants produced by the industrial work application.
No matter what pressure you are compressing the air to you will need to meet the standards if you are going to call it breathing air for human consumption. The one most applicable in the United States is the OSHA Standard 29 CFR 1910.134 (i) (1) which states in part: “Compressed breathing air shall meet at least the requirements for Grade D breathing air described in ANSI/Compressed Gas Association Commodity Specification for Air, G-7.1-1989, to include:
- Oxygen content of 19.5% – 23.5%;
- Hydrocarbon (condensed) content of 5 milligrams per cubic meter of air or less;
- Carbon monoxide (CO) content of 10 parts per million (ppm) or less;
- Lack of noticeable odor”
To meet the standard you will need to have an air filtration system consisting of multiple filters, as well as a carbon monoxide monitor. Both are needed for worker protection.
Because we are typically compressing atmospheric air to around 125 psi in an industrial compressor, we can expect to see about seven times the contaminants in the air stream as compared to the air we breathe directly. The amount of contaminants can vary greatly depending on where the source of the ambient air is being gathered from. Locating your compressor in a relatively clean environment will help your filters last longer, but you will need to check your filters for pressure drop often to know when the filter is getting clogged.
Some of the more popular air-breathing packages that meet the OSHA and ANSI standard are manufactured by Master Pneumatic (www.masterpneumatic.com), Sterling Heights, Michigan. Their Series 350, shown below and 380 size packages can supply low pressure breathing air to two or four users respectively.
These preassembled packages take the guess work out of what components are needed to meet the OSHA standard. The assembly will contain the following:
- Slide gate lockout
- General purpose filter to remove free water and particulate to 5 micron with 98% efficiency
- Coalescing filter to remove 99.98% of oil, aerosols and particulate down to 0.3 micron
- Activated Charcoal filter to remove odors and tastes
- Carbon Monoxide monitor
- Quick couplers for multiple user connections
- Wall brackets, relief valve, differential pressure indicator and pressure gage
A preassembled package makes it easy for an industrial site to convert compressed air already used for other applications in the plant to air that is able to be consumed by a person. A mask and a pressure demand respirator is used when working in an area that the air is not desirable to be inhaled because of contaminants.
I hope I have given you some information you can use to meet the standards for your breathing air. If you have any questions just reply to this post. I’d like to hear from you.