6.The troposphere is the layer of air in the 20-40 Km altitude range. Ozone is a primary pollutant. The amount of nitrogen dioxide in the atmosphere has decreased in the last 20 years. An oxidant is a substance that removes hydrogen from a compound. Carbon monoxide is a gray colored gas with an odor like rotten eggs.
Nasal hairs play a part in cleaning air before it reaches the lungs.
The beginning signs of an asthma attack include sweating and rapid pulse. During an airway spasm, the muscles of the alveoli contract and the membranes swell. There is a phenomenon called sick building syndrome. Cat saliva is considered to be a biological contaminant. The number of asthma cases since 1982 have decreased.