Human economic activity has led to the emergence of factors that destroy the ozone layer of the Earth. This layer is contaminated by nitrogen oxides, the sources of which are jet aircraft, space rockets and nitrogen fertilizers used in agriculture. A great danger to the ozone layer is the entry into the atmosphere of chlorine-containing substances, primarily chlorofluorocarbons, the so-called freons. Freons are practically harmless, they do not form explosive mixtures with air and do not react with most metals. Chlorofluorocarbons are used in refrigerators, air conditioners, and heat pumps as refrigerants; in the production of porous plastics and paints; for cleaning computer chips; for displacing the contents of aerosol cans and the manufacture of sterilizing medical solutions. Freons are dangerous for the environment in that some of them destroy the ozone layer of the Earth and lead to the formation of so-called ozone holes in the atmosphere. If their number and size increase, then this can lead to the death of many living organisms.
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