The "big red button" is generally associated with one of two operations:
1. EPO or Emergency Power Off.
EPO buttons generally cut power to part or all of the room it is located in, as you've described above. EPO can be used in any number of instances which are typically defined by the occupant of the room through some sort of procedure or inter-company process. With regard to fire protection, it is generally recommended that power be cut to the facility PRIOR to the discharge of any fire protection system. This would include both waterless (clean agents) and water-based (sprinklers) systems. In many system designs, the EPO operation is automatically tied in with the control systems. In other words, the system will automatically cut power to the room prior to discharging any agent or water, through the use of smoke detection and an intelligent control panel.
In practice, many companies do NOT want power cut to the facility for any reason. The decision whether to cut power or NOT cut power is typically left up to a discussion between the local authority and the building owner and/or occupant. The NFPA codes do not REQUIRE power to be cut, but generally recommends it, in several different standards.
The benefit to cutting power to the room is the elimination of the most common ignition source for a fire. With power continually present, the risk or reflash or reignition is more pronounced in the hazard area. The benefit to NOT providing EPO is a continuous operation of systems, with zero interruption. The owner / AHJ together must make the determination of when it is appropriate.
It is important to note that clean agents ARE PERMITTED and effective when used in a facility that has not cut power, but that additional agent may be necessary. Consult that NFPA 2001 standard for additional guidance.
2. System Abort.
An abort switch is used to delay the discharge of a clean agent system. Then audible or visual alarms indicate a discharge is imminent, the abort switch can be depressed to delay the discharge if it is known to be not needed or accidental. In most cases the abort switch does NOT prevent discharge, rather resets the countdown period (typically 30 seconds) such that the alarm or trouble can be cleared. It is good practice to have some sort of communication near the abort switch (phone or intercom) in order to alert others that help is needed. This is especially important if the switch is required to be depressed continuously (holding it down) in order to delay the discharge.
The benefit to depressing the system abort switch is simply to avoid an accidental discharge and the loss of agent contained in the system. It should be noted that if a fire is occurring, it is NOT recommended to use an abort switch. Let the system do its job!
This was first published in March 2006