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2024-03-11

Analysis of Dew Point Requirements of Medical Air

NFPA 99 (National Fire Administration) Medical Facility Standard (2005 version) is the current regulation according to which medical facilities in the United States design their compressed air systems. The NFPA 99 standard covers many of the requirements for medical gases, and compressed air is only part of the standard. To understand the full scope of the standard, including information on air compressor requirements.

Healthcare facilities have two separate compressed air systems that fall under NFPA 99. They are medical air and instrumentation air systems. They are two completely independent systems, which, according to the code, are not allowed to be connected. Both systems have specific dew point and air quality requirements. Both systems are monitored by specific local and master alarm systems. This paper discusses the medical air technology used to meet this standard.

Medical Air System

There are two types of medical air systems. Level 1 and Level 2 systems are defined from the NFPA 99 code:

Class 1 medical ducted gas and vacuum systems. A system used in situations where the occupancy of the tubing of a medical gas and vacuum system would put the patient at risk of morbidity or mortality.

Class 2 medical pipeline gas and vacuum system. Services use systems that interrupt in-line medical gas and vacuum systems, putting patients at a manageable risk of morbidity or mortality.

The medical air compressor produces medical air at an air pressure of 100 psig. This air is introduced at this pressure into a medical air dryer and filter. The pressure of the air was then reduced to 55 psig and distributed to residential areas for Class 1 or Class 2 applications. The pressure drop in the pipeline distribution is considered, and the final use pressure is 50 psig.

Medical air dew point

The dew point specifications for Class 1 and Class 2 medical air are the same. The NFPA 99 standard states:

"At any level of demand, medical air dryers should be designed to provide a maximum dew point below the frost point (0 C(32 F))."

"At any level of demand" is important. The NFPA 99 standard continues to state that the size of the dryer must be adjusted to provide the specified dew point at the calculated peak demand. Therefore, the calculated peak demand represents the full load condition for which the dryer must be sized. This allows the dew point quality to be maintained even when a crisis occurs and all air consuming devices are in use.

The reality in hospitals is that actual demand typically represents only 33% of peak computing demand. The 33 percent estimate is unofficial, but has been agreed by many industry experts. This means that an air dryer that must provide a dew point at "any demand level" must be able to provide a dew point of 32 F at 33% load.

Medical air dew point alarm

Medical air quality monitoring requirements are very specific in the NFPA 99 standard. They are summarized as follows:

Medical air quality shall be monitored downstream of the medical air regulator and upstream of the piping system as follows:

1. When the dew point under system pressure exceeds 4°C( 39 °F), the dew point should be monitored and local alarms and all master alarms activated.

2. Carbon monoxide should be monitored, and a local alarm should be issued when the CO content exceeds 10 ppm. [See 5.1.9.5.4(2).]

3. If the monitor loses power, the dew point and carbon monoxide monitors should activate the signal of individual monitors on all main alarm panels.

Therefore, the medical air dew point can be monitored both at the control panel of the dryer (at 100 psig pressure) and downstream after the pressure regulator (at 50-55 psig pressure). The presence of any moisture in the pipeline triggers a downstream alarm. There are many types of dryers available to eliminate moisture. Refrigerated membrane desiccant type dryer. All are able to comply with the NFPA 99 standard while facing various challenges.

Consult medical dryers, medical filters,Please contact our manager Zhang, telephone: 15822721002