34 Pa. Code § 47.161
Entrances to foundries shall be protected from November 1 to April 1 of each year by a covered vestibule, either stationary or movable, which shall be constructed so as to eliminate drafts and of such dimensions as to answer ordinary purposes, such as the passage of wheelbarrows, trucks and small industrial cars. This requirement does not apply to entrances used for railroad or industrial cars handled by locomotives or motors, or for traveling cranes, horse-drawn vehicles or automobiles. The entrances may remain open only for such time as is necessary for the ingress and egress of such cars, trucks, cranes, horse-drawn vehicles or automobiles. No locomotive shall remain inside the foundry during the loading or unloading of the cars.
34 Pa. Code § 47.161