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The paper deals with the ability of human olfaction to identify odours associated with thermal destruction of polymers. The investigations confirmed the ability of early detection of equipment overheating and subjective odour evaluation using the 5-point intensity scale and calculating the relation of odour intensity to the maximum admissible concentration of volatile chemical contaminants aboard piloted space vehicles. Emission of gases by polymers in electrical equipment starts with heating temperature rise to 100 degrees C. A new odour smelled by only some of humans due to individual perception signifies typically that emitted gases are below MAC for space vehicle. Odour sensed by everyone though not irritating signifies, as a rule, of chemical contamination above MAC but not contingency. Symptoms of irritation by products of thermal destruction of polymers signify contingency and require the use of personal protection equipment.

Comparative evaluation of Russian and foreign (NASA/USA) off-gas tests for polymers proposed for use onboard the NASA space vehicles was fulfilled with a polymer hardware model. Qualitative and quantitative composition of gases emitted in the model was determined with the gas-chromatographic technique. Data of the evaluation allow the suggestion that informational capacity of the NASA technique is insufficient for making conclusions on suitability of a polymer or a device for long-operating manned vehicles. Discussed are the options for development of a short-cut test method that might combine desirable characteristics of the methods practiced in two countries.

Local fire in an enclosed environment was simulated, and the composition and toxicity of compounds outgassed by the polymers were investigated. Highly toxic compounds, e.g. prussic acid, carbon monoxide, benzene, nitrogen oxides, formaldehyde, were identified. The toxic hazard of the products depended on the mass and chemical composition of the burnt materials, time of exposure and enclosure volume. In the case of a local fire the enclosed atmosphere should be monitored by rapid diagnostic methods using indicator tubes.

Time-temperature dependence of concentrations of outgasing products of polymers and rubbers was studied. Applying the principle of time-temperature equilibrium, the exposure time for a laboratory rapid study of polymers at 100 degrees C was estimated to be 1 hr for enamels, lacquers and dyes, 1.5 hr for block and sheet polymers, 2.5 hr for sealants and rubbers, and 4 hr for textile materials, measured from the time when the preassigned temperature was achieved. The rapid method can be recommended for preliminary chemical study of polymers at the stage of their laboratory testing.

Experiments were carried out to study the resistance of rats to an acute effect of ethylacetate vapors at concentrations of 25 to 69 g/m-3 after their 20-day exposure to hypokinesia and 20-day exposure to altitudes of 3200 and 5000 m. The effect of ethylacetate at concentrations of 47 and 10 mg/m-3 on the rats in a chronic 90-day experiments was also investigated. After an exposure to hypokinesia and hypoxia the sensitivity of the rats to an acute effect of ethylacetate vapors increased 2- or 3-fold. The chronic inhalation of the substance by the hypokinetic animals brought about disorders in the brain microstructure and renal pathology. The poisoned animals that retained normal motor activity displayed serious pathological changes in the thyroid gland. It is concluded that changes in the reactivity of the animal and human body to chemical agents must be taken into consideration when developing standards for the space cabin atmosphere.

In view of a wide use of polymers in the spacecraft interior and their potential hazard, a system of hygienic control over their safety at every manufacture stage has been introduced. The system includes: an analysis of a list of polymers; laboratory testing of samples under standard conditions; bench testing of various polymers used in the hardware and software under operational conditions; an examination of space cabin environments in real flights. The system of hygienic control allows selection of the safest polymers, i.e. those with minimum outgasing.

The rats trained to hypoxic hypoxia changed their resistance to the inhalation effect of dioxane and dichloroethane vapors. The training regimen (20-day continuous hypoxia at an altitude of 3,200 m and intermittent hypoxia for 6 hours a day amounting to 25 rises to an altitude of 5,000 m) influenced markedly the intoxication effect. Adaptation to hypoxia increased the alveolar-capillary surface of the lung parenchyma, thus enhancing a better entry of chemicals into the body. The posthypoxic pattern of the structural rearrangement of the pulmonary tissue was similar to that observed during moderate hyperoxia.

Ethyl acetate was studied as an atmosphere contaminant in an enclosed environment. A 90-day continuous experiment on 160 white rats and 120 white mice with three concentrations of the compound (43, 10 and 2 mg/m3) was carried out. Ethyl acetate used in the first two concentrations caused functional disturbances in the state of animals and morphological changes in their viscera. Ethyl acetate at a concentration of 2 mg/m3 was ineffective. The data obtained allow recommendations of permissible concentrations of ethyl acetate vapours in an enclosed atmosphere in relation to a different time of man's exposure.

Resistance of rats exposed to 20-day hypokinesia to high concentrations of vapors of ethylacetate, dioxan, and liquid fluorochlorocarbon was studied. As compared with controls, lethality of the hypokinetic animals increased upon ethylacetate and dioxan breathing and decreased upon intoxication with liquid fluorochlorocarbon. The hypokinetic animals showed decreased resistance to chronic effects of ethylacetate and perfluorated ester vapors (at a concentration of 10 and 100 mg/m3 for 90 and 30 days, respectively). This was suggested by functional and pathomorphological studies.

Toxic parameters of 1-4 dioxan were estimated to be for white rats during 4 hr inhalation LC16 = 40 mg/l LC50 = 46 (42.2 +/- 50.1) mg/l; LC84 = 52 mg/l; for white mice during 2 hr inhalation LC16 = 61 mg/l; LC50 = 65 (61.3 +/- 68.2) mg/l; LC84 = 69.5 mg/l. As a result of single and repeated application, 1-4 dioxan did not induce skin changes, it was rapidly absorbed into the blood, and led to acute poisoning and irritation of the eye mucosa. A 24 hr exposure of white rats to 1-4 dioxan at concentrations of 4 and 20 mg/m3 for 90 days brought about their delayed weight gain, increased activity of glutamate-aspartate and glutamate-alanine transminases, prolonged duration of narcotic sleep, elevated content of protein in the urine, decreased diuresis, changed content of chlorides and altered motor chronaxia. The above concentrations proved to be effective. 1-4 dioxan at a concentrations proved to be effective. 1-4 dioxan at a concentration of 0.5 mg/m3 produced slight threshold changes.

This review surveys the data on environmental effects upon toxicity of polymers used in the interior of manned enclosures. An integrated approach to the assessment of polymer safety is described which takes into consideration space flight effects on the migration of volatile chemicals into the cabin and which includes hygienic monitoring of them at different stages of spacecraft production. Hygienic requirements for the evaluation of nonmetallic materials are given.

The purpose of this study was to investigate the composition and toxicity of fluoroplastic F-40 thermodestruction products at 300-500 degrees C and to identify the maximally allowable temperature for their safe use. When heated over 400 degrees C, the products of luoroplastic F-40 evolution included such compounds as hydrogen fluoride, fluro-organic compounds, carbon monoxide, formaldehyde. When heated at 500 degrees C, the thermodestruction products caused the highest mortality rate of mice. The pathogenesis and clinical development of fluoroplastic F-40 poisoning are primarily associated with fluoro-compounds. It is concluded that the temperature 300 degrees C is the maximum temperature at which tetrafluroethylene-based polymers can be used.