Furnace room ventilation

are there general guidelines for ventilation in a closed furnace room . Ie is there a sf of ventilation per sf of room?

combustion air for a confined space requires two permanent openings to adjacent spaces is required. One opening must be within 12 inches of the top and one opining must be within 12 inches of the bottom of that confined space into adjoining rooms… Each opening must be at least 1 square inch per 1,000 Btu/h input rating of all appliances combined as a total Btu/h rating. Each opening must be at least 100 square inches as a minimum size if the calculation of Btu/h total allows smaller the 100 square inches must be met per opening.

Thanks Jeffery

Add btuh of appliances in room … divide by 1,0000 … multiply by 50 cubic ft

100,000 btuh furnace + 40,000 btuh water heater = 140,000 btuh / 1,000 = 140

140 x 50cft = 7,000 cubic ft of room needed. If so its an Unconfined Room and is large enough . If not its a Confined Room and needs more Combustion Air.

At that point there are multiple ways to get the needed C/A depending on house and room layout. If inadequate combustion air in room, this is a great way to get your clients a service call on their ENTIRE hvac equipment, etc