Toxicological investigation of Halotron IIB - a fire extinguishing tool to be used in sealed rooms

The fire extinguishing tool on sub-marines and ships must have good fire extinguising properties and low human toxicity. On behalf of the Swedish Defence Material Administration, FOI NBC Defence has performed a literature study and toxicological assessment of Halotron IIB, which is aimed to be used as a fire extinguising tool aboard Swedish naval ships. halotron IIB, which is analogous to Bejaros´ Halotron IIB, is a pressurized mixture of three gases, HFC-134a (tetrafluoroethane), HFC-125 (pentafluoroethane) and carbon dioxide. It is today a registered trademark of the American Pacific Corporation (AMPAC), USA. The total concentration of Halotron IIB needed to extinguish the fire must exceed 12.4 percentage by volume resulting in about 11 percentage by volume of hydrofluorocarbons (HFCs) in the air. The absorption of HFCs via the lungs to the blood is rapid and the steady state with inhaled air is reached within 15 minutes. the high solubility of the HFC compounds in fat will induce initial toxic effects associated to the nervous system and expressed as sedation. Both HFC compounds have a low acute toxicity, but HFC-134a was sedative to rats exposed to a concentration just above 10 percentage by volume. A whole-body exposure of volunteers to 0.8 percentage by volume of HFC-134a for 45 minutes induced no effects. The LOAEL and NOAEL values for HCF-134a are estimated to 7.5 and 5 percentage by volume respectively. The highest acceptable concentration during a 5-minute exposure period to HFC-125 is set to 8 percentage by volume. When using Halotron IIB on fire in an engine room, the body burden of HFCs may not reach levels high enough to become sedative during a rapid evacuation. It is known that the development of heat and toxic smoke from the fire in a room become highly dangerous within a couple of minutes. Therefore, exposure to the HFCs at concentrations twice that of NOAEL for less than 2 minutes is preferable since the extinguishing tool can fight the fire successfully and save lives.