Ventis HEI170 Fireplace Insert Wood Burning with Blower 144 CFM 65,000 BTU 1,800 Sq. Ft NewThe Ventis HEI170 is a medium sized wood burning fireplace insert designed for heating spaces from 500 to 1,800 sq. ft. The firebox measures 1. 9 cu. ft, and is lined with refractory bricks for better heat distribution. The HEI240 offers non catalytic combustion technology, and a stainless steel secondary air system which improves gas combustion. This unit has a maximum burn time of 6 hours and can hold logs up to 18 inches.