Light Duty High Input Direct Vent models are the solution for air tight installations. Utilizing a closed combustion and co-axial concentric (pipe inside a pipe) direct venting system, they are perfect for installations that lack sufficient air for combustion. They require no electrical power yet still offer sidewall venting. For installation flexibility, venting options include a solid telescoping extension that can accommodate up to eight ft vertically and eight ft horizontally and a flexible vent kit that allows installations from 44 to 100 in total length. Light Duty High Input Direct Vent models are also available in Ultra Low NOx Eco-Defender Safety System® versions.