A study was made on toxicity and hazards of 16 chladons which are representatives of various halogen derivatives of saturated hydrocarbons (fluorine derivatives of methane, ethane, propane, butane). It is shown that in terms of acute toxicity parameters, the studied chladons refer to low-toxic and low-risk substances (hazard class 4 according to GOST 12.1.007). The least toxic are fully fluorinated hydrocarbons: tetrafluoromethane, hexafluoroethane, octafluoropropane, decafluorobutane.` In the clinical picture of acute poisoning, signs of a narcotic effect prevail. Limit values Limac were determined for fluorocarbons in the range of 750-180 mg/l, for mixed fluorochlorinated hydrocarbons- up to 100 mg / l (45, 80 mg/l), for fluoriodohydrocarbns (pentafluoriodoethane) 10.5 mg/l. The main criteria tests were indicators of the state of the nervous and cardiovascular systems. Long-term exposure to the compounds studied (chladons Nos. 32, 125, 227, 218, 31-10) caused marked changes in the functional state of the nervous and cardiovascular systems, peripheral blood composition and metabolic processes. Hygiene standards for most tested chladons in the workplace air (MAC workplace) are approved at the level of 3000 mg/m3, hazard class 4;,vapors; in the atmospheric air of residential areas, the MAC. average daily of 10 (20) mg/m3 is set, and 100 mg/m3 for maximum single concentration (MAC.maximum single), reflective -resorptive effect, hazard class 4.