Concentrations of fluoroalkanes associated with cardiac conduction system toxicity.

When respiratory alterations associated with the inhalation of aerosol propellants were eliminated, it was demonstrated that a ten-minute exposure to trichloromonofluoromethane (Freon 11) at concentrations below 15% never caused death. Rarely, at a concentration of exactly 15% minimal sinus slowing occurred (change less than 10% the base line rate). At concentrations between 15% and 17%, nine animals survived while seven succumbed. Ranges between 17.5% and 21% resulted in seven survivors of 19 animals, while no animal survived a ten-minute exposure to a concentration in excess of 21%. The mode of death was most commonly and ultimate asystole. Concentrations of dichlorodifluoromethane (Freon 12) greater than 95% were necessary to produce death in ten minutes, and severe oxygen deficit was evident.