Boiler 4 : A closed vessel in which water is heated, steam is generated, steam is superheated, or in which any combination thereof takes place by the application of heat from combustible fuels, in a self-contained or attached furnace
NFPA 31 Standard for the Installation of Oil-Burning Equipment, 2001 ed. https://www.nfpa.org/Assets/files/AboutTheCodes/31 /LPI-AAA_ROPagenda_06-09.pdf, (Std: Install of Oil-Burn Equip - Amer) {195 NFC}