Safety fan
means:
(1) a reversible axial fan in cylindrical housing that is designed and marketed for use in ducted tunnel ventilation that will reverse operations under an emergency ventilation condition;
(2) a fan for use in explosive atmospheres tested and marked according to ISO 80079-36:2016, Explosive atmospheres -- Part 36: Non-electrical equipment for explosive atmospheres -- Basic method and requirements;
(3) a Positive Pressure Ventilator; or
(4) fans complying with ANSI/UL 705 (August 23, 2021) Standard for Safety for Power Ventilators and listed as “Power Ventilators for Smoke Control Systems