![]() It is recommended that any air supply system be designed to deliver greater than the minimum required (4 cfm for tight fitting facepieces and 6 cfm for hoods), but the flow should be adjusted so as not to be so high as to be uncomfortable for the wearer. Disconnect the tube from the facepiece and insert into a calibrated rotameter or other airflow measuring instrument, and then, the line pressure may be adjusted to obtain the desired airflow. The end of the breathing tube is the best point at which to take the flow measurements. The high-pressure air hose plugs into this valve, and a low-pressure breathing tube runs to the facepiece or hood. In most systems, there is a belt-mounted valve or regulator. The lengths of hose required for the job should be connected. This is most easily done during the set up of the system before work begins. ![]() In addition, the user has the option of measuring the airflow at the respirator. A much better approach would be a system where individual control is provided with a separate regulatory and pressure gauge for each user. In this case, it is difficult to determine if each user is receiving the required airflow. If each user has different hose lengths or respirators with different air pressure requirements, this manifold arrangement should not be used. Problems may develop when more than one user is connected to an air manifold with a single regulator and pressure gauge. If the appropriate pressure for the total length of hose is used, ample flow should be available. Concern with the latter is because of the considerable pressure drop in the quick-connect fittings between each section of hose. Manufacturers of airline respirators include instructions specifying a range of air pressure required to produce the needed flow rates based on both the lengths of hose used and the number of sections connected together. An exception would be for work at high altitude, such as above 6000 ft at Los Alamos, where the atmospheric pressure is less than 80% of sea level, requiring corrections for the difference in flow. ![]() Therefore, one needs to be concerned only with the airflow at ambient conditions.įurthermore, the temperature and pressure at most actual working conditions are sufficiently close to standard conditions that either may be used for the calculations. It is the airflow about the head and face of the respirator wearer that largely determines the protection provided by the device. There appears to be a misunderstanding on what flow measurement is appropriate when adjusting the air pressure on an airline. The airflow requirements of regulator-controlled airline respirators (such as pressure-demand) are so much less than continuous-flow devices, that adequate airflow is not usually a problem. This discussion is limited to continuous-flow Type C respirators. In response to a Regional inspector's request, the Los Alamos National Laboratory (LANL) was asked how IE can be assured that required minimum airflow is being provided to each individual respirator user when several users are sharing a standard air regulator manifold supply. It provides guidance on assuring that the required minimum airflow is being provided to each individual respirator user when several users are sharing a single air regulator manifold supply. Joyner (and others) dated August 5, 1982. Airflow Measurement and Control for Supplied-Air Respirators HPPOS-118 PDR-9111210275 ![]()
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