Air Conditioning: is the control of weather Within a chamber so as to make it comfortable. Average comfort condition is temperature 18°C; relative humidity 60-65 percent; air movement 25-75 ft/sec; introduction of 25 percent fresh air; purification of air and deodorizing.

Davy’s safety lamp is an oil lamp whose chimney GPs made of wire gauze. A part of the heat of the flame transmitted to the gauze goes out by convection and radiation to the surrounding medium. If explosive gases like methane burn inside the lamp, the fire does not come out as the wire gauge absorbs most of the heat and the temperature outside does not reach ignition point.

Thermos flask is a double-walled bottle with silvering on the inner side of each wall with vacuum in between. Any substance, hot or cold, put inside the flask remains so for a considerable period as there is no exchange of heat due to radiation because of the silvering nor due to conduction or convection. Vacuum is a non-conductor and non-medium. Thermos flask is generally used for preserving hot tea, coffee or ice, cold drinks, etc.