875—91.13 (89) Air and ventilation. A permanent source of outside air shall be provided for each room to permit satisfactory combustion of fuel and ventilation if necessary under normal operations.
The minimum ventilation for coal, gas, or oil burners in rooms containing objects is based on the Btu’s per hour, required air, and louvered area. The minimum net louvered area shall not be less than 1 square foot. The following table shall be used to determine the net louvered area in square feet:

INPUT
(Btu’s per hour)	MINIMUM AIR REQUIRED
(cubic feet)	MINIMUM LOUVERED AREA
(net square feet)	
500,000	125	1.0	
1,000,000	250	1.0	
2,000,000	500	1.6	
3,000,000	750	2.5	
4,000,000	1,000	3.3	
5,000,000	1,200	4.1	
6,000,000	1,500	5.0	
7,000,000	1,750	5.8	
8,000,000	2,000	6.6	
9,000,000	2,250	7.5	
10,000,000	2,500	8.3	
When mechanical ventilation is used, the supply of combustion and ventilation air to the objects and the firing device shall be interlocked with the fan so the firing device will not operate with the fan off. The velocity of the air through the ventilating fan shall not exceed 500 feet per minute and the total air delivered shall be equal to or greater than shown above.