Most technical arguments in a theatre are between departments. This one is not. The requirements governing how people leave a building are imposed from outside, they are not negotiable by the production, and a design that conflicts with them loses.
Everything below describes general principles. Fire and life safety requirements differ by country and frequently by municipality, they change, and the applicable rules are those enforced for the specific building by its authority. Nothing here is advice, and none of this work belongs to anyone other than the qualified people responsible for it.
There is no true blackout
A room that people must be able to leave in an emergency keeps its exit routes identifiable at all times. Exit signs stay illuminated, emergency luminaires stand ready to operate on loss of supply, and aisles and steps remain marked.
The consequence for design is direct: the deepest darkness available is the darkness that remains when all of that is still on, and it is not very deep. Productions that plan a total blackout as a dramatic device are planning something the building does not offer, and finding out during a technical rehearsal is finding out at the worst moment.
Some codes permit exit signage to be reduced in brightness during a performance in an assembly space, under specified conditions and with automatic restoration on alarm or loss of power. Where that is available it is a system to be designed and commissioned rather than a switch, and whether it applies is a question for the authority rather than for the lighting designer.
The auditorium's geometry is fixed before the set is drawn
Aisle widths, the number and location of exits, seating capacity and the distance a person may have to travel to reach a way out are set by regulation, and they determine what the room can contain. A set that extends into an aisle, a temporary seating bank that changes the exit pattern, or an audience seated on stage all alter the calculation the building was licensed against.
These are not obstacles to design so much as parameters of it, in the same way that the height of the grid is. Knowing them at the model stage means designing something that can be built.
Haze interacts with the systems that protect the building
Atmospheric effects make light visible and are fundamental to a great deal of lighting design. They also reduce visibility along escape routes and can be detected by the building's fire detection system as smoke.
The reconciliation is procedural and belongs to the venue: detection arrangements adjusted or supervised under an agreed procedure, with the authority informed, for defined periods, with someone responsible. It is never a matter of a technician deciding to cover a detector, and a production that arrives expecting haze without having asked should expect the answer to be no.
Effects that act on the audience directly
Strobing and rapidly flashing light can provoke seizures in people with photosensitive epilepsy, and the standard response is advance warning at the point of sale as well as at the door, so that a patron can decide before they have travelled and paid. Guidance on flash rates exists in broadcast and public information standards published by regulators and standards bodies rather than by equipment makers.
Lasers directed anywhere near an audience are regulated separately in most jurisdictions and are operated by people qualified and permitted to do so. This publication does not describe that work.
The house lights are a cue with two owners
Bringing the house to black is a lighting cue, and bringing it up at the end is a safety operation, and the same fader does both. That is why control of the house lights is usually shared: the console can take them down, and there is an independent means of bringing them up that does not depend on the console being alive.
The scenario the arrangement exists for is unglamorous and does happen: a console failure during a performance, in a dark auditorium, with several hundred people who now need to leave. Emergency lighting covers the escape routes; it does not make the room usable. A production that has moved every part of house light control into a single show file has removed the second owner without noticing.
The person who decides is not in the production
Every one of these questions is ultimately answered by the authority responsible for the building: a fire officer, a licensing authority, a building control body, depending on the country. They can require changes at any point, including after a production has opened.
The practical lesson is about timing rather than about rules. A design presented early, with the intended effects described honestly, produces conditions that can be worked with. The same design presented at the technical rehearsal produces a refusal, because at that point there is no time to design an alternative.
What we cannot verify
Requirements vary by jurisdiction and are enforced by local authorities whose interpretations also vary; the general descriptions here are not a statement of any specific rule and must not be used as one. Product claims about emergency lighting duration, signage performance and detection compatibility come from manufacturers. The competent sources are the applicable code, the venue's own fire risk assessment, and the authority having jurisdiction over the building.
The short version
- Egress requirements come from outside the production and are not negotiable by it.
- Exit signage and emergency lighting stay on, so a true blackout is not available.
- Aisle widths, exits, capacity and travel distance are parameters of the design.
- Haze interacts with fire detection, and the procedure belongs to the venue.
- Flashing effects need warning at the point of sale, not only at the door.
- A design shown early gets conditions; the same design shown late gets a refusal.