Environmental test chambers and rooms are used to ensure the reliability of industrial products, especially electronic items, through prolonged exposure to one or more environmental parameters. They provide heating and/or cooling and often include an analog meter, digital readout, or video display with test results. Some environmental test chambers and rooms subject samples, components, or products to extreme temperatures, thermal cycling, or extreme humidity. Others monitor emissions from devices such as internal combustion engines under carefully controlled conditions. Chambers for the electro-dynamic and mechanical vibration testing of machinery are available. Environmental test chambers and rooms that measure corrosion monitors the effects of variables such as heat, humidity, salt fog, salt spray, and rain spray.