14.151—Primary enclosures.

(a) Except as provided in § 14.106(j), ventilation openings must be located on at least two walls of a primary enclosure. When the required ventilation openings are located on two opposite walls of the primary enclosure, these ventilation openings shall comprise at least 16 percent of the total surface area of the ventilated wall. When ventilation openings are located on all four walls, the openings shall comprise at least 8 percent of the total surface area of each wall. At least one-third of the total minimum area required for ventilation of the primary enclosure shall be located on the upper one-half of the primary enclosure.