… for future reference:
- Your local Gas Codes will require meeting their combustion and relief air openings as well. For example, the local Gas Codes where I am require the following for installations with less than 400,000 Btuh Input total:
" When an appliance is located in a confined space and the air supply is from the outdoors, the space shall be supplied with two permanent openings that communicate directly to the outdoors by means of openings or ducts. The openings or ducts shall conform to:
(i) Lower Opening - 1 sq. inch per 2000 btuh Total Input rating of the appliances in the space when the means of communicating air to the outdoors is by means of a horizontal duct, or
(ii) Lower Opening - 1 sq. in. per 4000 Btuh of the total input rating of the appliances in the space when communication to the outdoors is directly by an opening, or by means of a vertical duct, and
(iii) the upper opening shall be located as near the ceiling as is practical, but not lower than any relief opening of a Draft Hood or Draft Regulator, and shall have a free area of not less than the total area of all vents and chimneys from the appliances contained therein…"
Basically you have to have a low level combustion air inlet to the room as well as a high level relief vent. The Code requirements are somewhat based on the basic combustion formulas, but with saftey factors. Check your local Codes for what they require first."