Compressed Breathing air is produced by a breathing air compressor and purification system. The air protects workers engaged in tasks like sandblasting, spray painting, chemical spill clean-up, welding, grinding, pipe and tank cleaning and similar activities where repeat exposure can pose a health threat.

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In the code of Federal Regulations, Title 30, Chapter 1, Part II, the Department of Labor defines the atmospheres where compressed breathing air should be used as those "which may produce physical discomfort immediately, chronic poisoning after repeat exposure, or acute adverse physiological symptoms after prolonged exposure."

In the United States, the Occupational Safety and Health Act (OSHA) requires Grade D breathing air "OSHA supplied breathing air". The Compressed Gas Association developed and published the Grade D breathing air standard (G-7.1.) The standard was last updated in 1989. In Canada the standard is set by the Canadian Standards Association (CSA).

In addition to contaminant maximums compressed air temperature safety shut-off switches, carbon monoxide detectors, and pressure regulators are required to produce Grade D compressed breathing air. Breathing air systems do not add oxygen to air, so it is crucial that intake air is taken from a source free of exhaust and other contaminants.

Typically, compressed breathing air is produced using a breathing air compressor, aftercooler, dryer, catalytic converter, adsorber, and filter to purify the air. A refrigerated dryer or a desiccant dryer can be used. (figure BA1-1)

Types and functions

Compressed breathing air system used in industry, constant flow works in the most harmful, and most toxic environments. Purified air is constantly swept through a worker's personal respirator. An advantage of constant flow is it minimizes the amount of outside contaminants that breach the respirator.

Constant Flow
As the most common type of compressed breathing air system used in industry, constant flow works in the most harmful, and most toxic environments. Purified air is constantly swept through a worker's personal respirator. An advantage of constant flow is it minimizes the amount of outside contaminants that breach the respirator.

Demand Flow
The worker opens and closes a valve by his breathing, letting breathing air in when inhaling and shutting the valve while exhaling. The exhaled air is vented to atmosphere. Demand flow systems are effective in conserving air and are often used with compressed air cylinders. One disadvantage is that the negative pressure within the respirator during inhalation can allow leakage and contamination. Tight-fitting, personal respirators are used with demand flow systems.

Pressure Demand
Pressure demand systems supply constant positive pressure to the personal respirator. When the worker inhales, more air is supplied to meet the workers need. The continuous positive pressure allows this system to be used in applications where toxic contaminants are present. Like demand flow systems pressure demand systems require tight fitting personal respirators.

Breathing air purifier sizing and selection recommendations Cartridge Breathing Air Purifier

Disposable

The filter (fig. BA1-3) removes liquid oil and gaseous hydrocarbons levels below the ANSI specification. Filters do not remove carbon monoxide. Most manufacturers offer carbon monoxide detectors that can be installed to monitor the compressed air's carbon monoxide level. Most ambient air and untreated compressed air meet the Grade D breathing air requirements for carbon dioxide and oxygen. Filters do not affect or improve carbon dioxide or oxygen levels. Most manufacturers recommend changing breathing air filters at a minimum of every 2,000 hours.

Filters are a good choice for breathing air systems when a plant only requires breathing air occasionally. When a plant needs a constant supply of breathing air, element replacement cost is prohibitive compared to operating a continuous duty desiccant or refrigerated breathing air systems.

Sizing is dependent on inlet flow (scfm)(m3/min.) and inlet pressure (psig)(bar). The air must be cooler then the filter's maximum temperature, typically 120°F (49°C) for breathing air filters.

Continuous-duty Desiccant Breathing Air Purifier

• Filter - removes oil, water, and solids
• Desiccant Dryer - reduces the relative humidity
• Catalyst - converts carbon monoxide to carbon dioxide
• Carbon Filter - eliminates undesirable tastes and odors

To size a continuous-duty desiccant breathing air purifier, first determine whether you require a portable purifier or a larger stationary unit. Portable units can deliver up to 150 scfm. Stationary units can be sized from 100 scfm (2.8 m3/min.) to 1000 scfm (28 m3/min.).

Most manufacturers publish sizing information based on an inlet temperature of 100°F(38°C) at 100% humidity. Higher inlet temperatures reduce purifier capability. If your air system delivers air below 100°F (38°C), size the system to meet your breathing air scfm requirement based on your inlet pressure. If the temperature of the air is above 100°F (38°C) at the purifier inlet, a temperature correction is required to properly size the system.

Refrigerated Breathing Air Purifier
Refrigerated Breathing Air Purifier's (fig. BA1-5) for example the Pyramid 8000, consists of the following:

• Chiller-condenses water and hydrocarbon vapors
• Coalescer-removes aerosols, water, oil, and condensate
• Adsorption filter-eliminates undesirable tastes and odors
• Heat Exchanger-heats the air and catalyst. Another heat exchanger cools the air.
• Catalyst-converts CO to CO2
• Particulate filter-removes fine particles

To size a Refrigerated Breathing Air Purifier, determine the adjusted flow:

• Inlet air temperature (°F)( °C)
• Inlet air pressure (psig)(bar)
• Ambient air temperature (°F)( °C)
• Required outlet flow (scfm)(m3/min.)

Adjusted Flow = Required Outlet Flow / Pressure Correction Factor

If your maximum ambient temperature exceeds 100°F (38°C), divide the adjusted flow by the ambient air correction factor for a new adjusted flow.

New Adjusted Flow = Adjusted Flow / Ambient Air Temperature Correction Factor

Once you have an accurate adjusted flow, select the model rated to handle that flow rate (scfm)( m3/min.). Refrigerated Breathing Purifiers can only be sized to 150 scfm (4.2 m3/min.). If you require a higher flow (scfm) (m3/min.), size a Continuous-duty Desiccant Breathing Air Purifier.

Installation and Maintenance recommendations Cartridge Breathing Air Purifier

Disposable
Install in the air system upstream of the workers. Be sure the filter is installed at a pressure and temperature below its maximums.

Maintenance:

• Inspect daily and change element based on color change. Do not exceed 2,000 service hours.
• Drain element housing daily to remove condensate build-up.

Continuous-duty Desiccant Breathing Air Purifier
Install the purifier where the ambient temperature is between 35°F (1.6°C) and 100°F (38°C). Inlet air must be free of liquid water. Liquid water will result in unsafe breathing air. The breathing air compressor upstream of the purifier must have a properly maintained aftercooler and separator with a drain valve to eliminate liquid water. The inlet temperature to the purifier cannot exceed 100°F (38°C). Protect the purifier from forklift or other moving machinery. If there is any floor vibration from heavy equipment or other source, bolt the purifier to the floor.

Support all piping running to the purifier. Do not allow the weight of any pipe to rest on the purifier. The purifier requires electricity. Wire the purifier according to the user manual.

Maintenance

Refrigerated Breathing Air Purifier
Leave enough space around the purifier to allow circulation of cooling air and easy maintenance. Protect the purifier from moving equipment like forklifts and locate it on level ground. Install it indoors where the ambient air temperature is between 50°F (10°C) and 100°F (38°C). Do not operate the purifier outside of the ambient air temperature range. Doing so can cause illness or death.

The Refrigerated Breathing Air Purifier requires both air system piping and electrical hook-up. The air from the breathing air compressor upstream of the purifier must have a properly maintained aftercooler and separator with a drain valve to eliminate liquid water.

Maintenance

Browse our selection of Breathing Air Dryers and Breathing Air Compressors online. If you have questions or can't find what you are looking for online, call our knowledgeable customer service team toll-free: 866-650-1937.