NASA Develops Breathing Unit for Full 30 Minutes of Fireground Work
A prototype self-contained breathing apparatus that weighs less than comparable units now in use and is designed to last 30 minutes under fireground working conditions has been developed by the National Aeronautics and Space Administration.
The unit, now midway through the system development phase, was described by Maurice A. Carson of the Johnson Space Center in Houston in talks at both the urban and industrial and federal workshops at the IAFC conference in Baltimore in October. Carson, who manages the NASA fireman’s breathing system program, said that breathing air can be stored at a maximum of 4000 psi in either 40 or 60-scf aluminum cylinders wrapped with fiber glass.
The weight of the apparatus with the large cylinder is 26 pounds and with the small cylinder, 20 pounds. Breathing apparatus with 45-scf cylinders weigh about 33 pounds and, Carson said, the weight of the NASA unit with the small cylinder compares favorably with sling breathing apparatus using 25-scf cylinders.
The NASA unit, like those used in the fire service, uses an open loop system with exhaled air discharged to the atmosphere and is superior to the closed loop system in all areas except weight and profile,” Carson commented. However, he regarded the weight of the NASA prototype as acceptable. The aluminum air bottle weighs about half the weight of a comparable steel cylinder.
Carson said that human factors also were considered in developing the NASA unit. These factors included comfort, ease of donning and doffing, less encumbrance, effective low-air warning and minimized breathing resistance.
The apparatus has a two-stage regulator. The first, or pressure-reducing, stage is on the back frame and the light second stage demand regulator is on the face mask. The demand regulator can be easily detached from the mask by operating a release lever. Removal of the regulator leaves a hole through which the wearer can breathe ambient air. The breathing apparatus has nothing on the front or side of the wearer’s body to interfere with his movements, Carson explained.
Net secures facepiece
A nylon net with one adjustable strap holds the facepiece in place. Carson commented that the net over the wearer’s head made it easier to don the facepiece quickly and reduced the interference of the mask with a helmet.
The facepiece is bubble-shaped, which reduces the total size of the mask and also minimizes helmet interference at the forehead. An oral-nasal deflector in the mask is designed to reduce mask fogging during exhalation. In addition, the demand regulator works with a spray bar that channels inlet air flow over the mask during inhalation to clear any slight fogging that might develop.
A whistle mounted on the mask warns of low air supply and sounds only when the wearer inhales, thereby conserving the diminished air supply.
NASA has already received deliveries under contracts to Martin Marietta to develop the 40-scf air cylinder and to Structural Composites Industries for the 60-scf cylinder.
Development of the breathing apparatus system, with the exception of the cylinders is being done under contract by Scott Aviation.
An oil-free, diaphragm-type compressor for the 4000-psi cylinders, an air purification system, a cascade air storage system and cylinder-charging equipment have already been delivered to the Johnson Space Center by the American Instrument Company.
Field evaluation of the breathing apparatus is scheduled to be conducted during the first half of the coming year. NASA will monitor the system performance and provide training and maintenance support. If the evaluation is favorable, a final report will contain system specifications that fire departments can use as a guide for buying this type of breathing apparatus, Carson said.
He stated that cost analysis indicated that if there is sufficient demand for the prototype breathing apparatus, the cost should be only slightly more than existing equipment.