If something gives off or gives out a gas, heat, or a smell, it produces it and sends it out into the air. natural gas, which gives off less carbon dioxide than coal
have as a by-product; "The big cities gave off so many wonderful American qualities
have as a by-product; "The big cities gave off so many wonderful American qualities"
give off, send forth, or discharge; as of light, heat, or radiation, vapor, etc ; "The ozone layer blocks some harmful rays which the sun emits"