Sidewall or Through-Wall Venting : A mechanical means applied to a nearly horizontal venting system to remove combustion products without benefit of a chimney or significant natural draft
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}