The Use of Cryogenic Air in Supplied Air Respiratory Protection

The Mine Improvement and New Emergency Response (MINER) Act of 2006 implemented new regulations in the underground coal mining industry that allow for the certification of non-compressed gas equipment for respiratory protection in underground coal mines. NASA’s Kennedy Space Center (KSC) Biomedical Research and Engineering Laboratory (BRL) is investigating the potential to expand cryogenic air supply systems into the mining and general industries. These investigations have, so far, resulted in four separate comparison and hardware development programs. The Propellant Handlers Ensemble (PHE) and Level “A” Ensemble Comparison (LAE): This study compared worker thermal stress while using the industry standard Level A hazardous material handling ensemble as opposed to using the similarly protective Propellant Handler’s Ensemble (PHE) that utilizes a cryogenic air supply pack, known as an Environmental Control Unit (ECU) as opposed to the compressed air Self Contained Breathing Apparatus (SCBA) used in the LAE. The research found that, in a 102°F environment, test subjects experienced significantly decreased body temperature increases, significantly decreased heart rate increases, and decreased sweat loss while performing a standard work routine while using the PHE, compared to the same test subjects performing the same routine while using the LAE. The Cryogenic Refuge Alternative Supply System (CryoRASS) project: The MINER Act of 2006 requires the operators of underground coal mines to provide refuge alternatives that can provide a safe atmosphere for workers for up to 96 hours in the event of a mine emergency. The CryoRASS project retrofitted an existing refuge chamber with a liquid air supply instead of the standard compressed air supply system and performed a 96 hour test. The CryoRASS system demonstrated that it provided a larger air supply in a significantly smaller footprint area, provided humidity and temperature control, and maintained acceptable oxygen and carbon dioxide levels in the chamber for the required amount of time. SCBA and Mine Rescue System (CryoBA/CryoASFS) Another requirement of the MINER Act is that additional emergency breathing equipment must be staged along evacuation routes to supplement the Self Contained/Self Rescue (SCSR) devices that are now required. The BRL has developed an SCBA known as the Cryogenic Breathing Apparatus (CryoBA), that has the ability to provide 2 hours of breathing air, a refill capability, and some cooling for the user. Cryogenic Air Storage and Filling Stations (CryoASFS) would be positioned in critical areas to extend evacuation time. The CryoASFS stations have a significantly smaller footprint and larger air storage capacity to similar compressed air systems. The CryoBA pack is currently undergoing NIOSH certification testing. Technical challenges associated with liquid breathing air systems: Research done by the BRL has also addressed three major technical challenges involved with the widespread use of liquid breathing air. The BRL developed a storage Dewar fitted with a Cryorefrigerator that has stored liquid air for four months with no appreciable oxygen enrichment due to differential evaporation. Testing of liquid breathing air was material and time intensive. A BRL contract developed a system that only required 1 liter of air and five minutes of time compared to the 10 liters of air and 75 minutes of time required by the old method. The BRL also developed a simple and cost effective method of manufacturing liquid air that joins a liquid oxygen tanker with a liquid nitrogen tanker through an orifice controlled “Y” fitting, mixing the two components, and depositing the mixed breathing air in a separate tanker.

The Effect of Respirator Wear on Blood Lactate During Maximal Exertion

The impact of a filtering half-face respirator and a half-face supplied air respirator use on blood lactate production was assessed during maximal exertion to determine if anaerobic strain increased compared to no respirator use. Twenty-eight participants performed a 30 second cycling Wingate anaerobic test (WAnT) wearing a half-face respirator. Blood lactate production was measured to evaluate if there was an increase in anaerobic strain from wearing a tight fitting half-face respirator compared to wearing no respirator. A supplied air respirator WAnT was then performed using 18 participants from the first experiment to evaluate if supplied air decreased anaerobic strain. Data from both experiments were compared to evaluate differences in the physiological effects due to respirator use during maximal exertion. A survey was administered following the second WAnT experiment to measure the participants' perception of acceptability and impact of supplied air respirator use in workplace. The blood lactate levels measured directly after the WAnT yielded lower overall mean values during the half-mask respirator trial (12.1 mmollL) and supplied air respirator trial (12.2 mmollL) than the no respirator trial (13.1 mmoI/L). However, differences in blood lactate levels were not statistically significant (p =0.597). Participants reported an average acceptability of 92.3% to wearing the supplied air respirator while performing light work. However, the average acceptability decreased as the exertion increased to moderate (78.8%) and heavy (46.6%) workloads. The supplied air respirator used provided no significant reduction in anaerobic strain within this study group compared to either the filtering half-face respirator or the no respirator condition. However, there were differences in physiological effects of respirators on each gender identified in this study. Further assessment of the anaerobic impact of respirators on each gender should be conducted.