26. Entry conditions: No person shall enter any furnace when its temperature exceeds 50 ºC, except if:(a) the workmen wear an aluminized suit, wool clothes or other equivalent protective clothing;
(b) ventilation is provided to reduce radiant heat inside the furnace and if standards for heat stress conform to the Threshold Limit Value of Physical Agents prescribed by the American Conference of Governmental Industrial Hygienists (ACGIH-1972);
(c) under the continuous supervision of a workman.