The confined space shall be provided with two permanent openings communicating directly with other spaces of sufficient volume so that the combined volume of all such spaces meets the criteria for an unconfined space. The total input of all fuel burning equipment installed in the combined spaces shall be used to determine the required minimum volume.
Each opening shall have a minimum free area of not less than 1 in.
2
/1,000Btu/hr (2120 mm
2
/kW) of the total input rating of all fuel burning equipment in the confined space, but not less than 100 in.
2
(0.06 m
2
). One opening shall be within 12 in. (300 mm) of the top of the enclosure, and one opening shall be within 12 in. (300 mm) of the bottom of the enclosure. The minimum dimension of air openings shall be not less than 3 in. (8 cm).