What are they?  Smoke vents are doors or hatches above the stage that, in the event of a fire, are designed to open automatically.  They’re typically either spring actuated (if they open upward) or gravity actuated (a typically older style that falls outward).  Visualize a typical stage cut through the centerline–it bears a striking resemblance to  a fire place with the audience chamber as the hearth and the fly tower as the chimney.  Open the vents and it behaves very much like one, also.

An interesting book that touches on this subject is John Ripley Freeman’s book “On the Safeguarding of Life in Theatres.”  This book is available for reading online through Google Books.  Freeman was a mechanical engineer who did a thorough review of the Iroquois Theatre fire in 1904.  Among the many things that went wrong at the Iroquois, the smoke vents failed to operate.  It was later determined that the contractor had failed to remove nails holding them shut.  Keep in mind that cooling in theaters of this era was generally natural air movement–windows or vents low down allowed fresh air in and fans or vents at the ceiling pulled it out.  The Iroquois had vents at the very back of the uppermost balcony.  This combination of factors allowed a deadly sequence of events to unfold as the fire spread throughout the fly space into all of the hanging scenery:

• Stagehands attempted to deploy the fire curtain (“asbestos”).  It caught or jammed partway down and did not fully cover the proscenium opening.
• Theatere staff, attempting to save the lives of the performers and workers on stage, opened the large loading door to the stage.
• The sudden rush of oxygen immediately caused a massive increase in the size, heat and power of the fire.
• The open vents at the rear of the balcony provided a “chimney” for the smoke and gasses–helping to pull them into the auditorium and out of the stage rather than up and away from the audience.

In the end, the vast majority of the deaths in the auditorium itself were in the uppermost balcony.  As in most fires, the majority of these people did not burn: they were suffocated.

Freeman’s conclusion was that if the smoke vents had operated properly, almost all of the audience would have walked out of the Iroquois Theatre.

Smoke vents are only one of several fire safety devices commonly found on stages.  Coming soon: information on interesting new research into what works–and what doesn’t.