All rooms in which Class I flammable liquids are used in open vats, pans or other vessels, or in which any flammable liquids are heated or otherwise treated in such a manner as to produce flammable vapor, shall be ventilated as hereinafter provided. There shall be a vent opening in the wall at the floorline near each open receptacle and each heating device containing such liquid. Such vent openings shall have a net cross- sectional area of not less than 32 square inches and shall be protected with one-half-inch mesh No. 16 wire. When such vent openings are not located in the outside wall of the building or room, there shall be a noncombustible vent flue built into the wall or floor or securely fastened thereto and so arranged as not to be subject to mechanical injury. Such vent flue shall conduct to and pass through an exhaust fan, which shall run continuously while the room is in use, and which shall be sufficient capacity to change the air in the room completely in not more than five minutes. All discharge outlets of such vent flues shall be provided with noncorrodible wire screen and shall be so located that they are not nearer than ten feet vertically or five feet horizontally from any door or window opening.
(Prior code § 129.1-43)