Data for False Activation in Pre-Action Systems?

11/18/2025

Could anyone point me to statistics to show how likely a single interlock pre-action sprinkler system is to spuriously or falsely activate?

A client is concerned about possible water damage in a high-voltage switchroom that could damage their gear and cause a lengthy business interruption.

I have tried examining NFIRS data, but its format makes it difficult to analyze without a background in relational databases. I would like to explain the relative risk to the client in terms of 'it's a 1 in 100,000-year event you are concerned about' or whatever the stats point to.

Thanks in advance.

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7 Comments

Ricardo Gonzales

11/18/2025 08:39:58 am

This would be a situation where I would have a sit down with the AHJ to eliminate the sprinkler system and put in a clean agent system. Contact NFPA and ask about their Electrical Danger data base. That may help.

High voltage and water have an explosive relationship and the discussion is well worth having. I recommend having an Electrical Engineer in the discussion as well as getting one of the State Electrical Inspector Supervisors in the meeting.

The NEC and NFPA 70E are adamant about Arc Flash protection and water with HV tend to go beyond Arc Flash dangers while energizing the wet room.

Usually there is no sprinkler in rooms with more than 600V. (AC or DC) and usually higher voltages are handled in an outdoor yard situation.

Josh

11/18/2025 09:22:30 am

I'm with you on this one. You'd have to convince ME to put any type of water delivery system in a room like that.

The potential loss of the HV system and the costs associated with that would outweigh the costs of a gas/clean agent system if it were my building.

matt

11/19/2025 02:31:06 pm

Thanks, appreciate the comments. My workscope is actually to do a risk analysis and evaluate for the client choosing between a pre-action system, gas flood or nothing in their HV room. (rest of the building will be sprinkler protected). Without running numbers, leaning already towards gas flood :) Will look into arc flash detection/protection...

Mark

11/18/2025 09:23:08 am

NFPA 2001 Clean Agents states over 480 volt design should be based on fire test. Manufacturers have not done any full scale tests. FM Global does have criteria in loss prevention sheet 4-9.

If they can shunt trip power before system discharge the over 480 design does not apply.

NFPA 12 addresses design for CO2 on high voltage but do have life safety issues (although the FM Global high voltage high concentration designs have life safety issues as well).

For sprinklers if shunt trip is option I would do that when detection goes into alarm or on valve discharge pressure switch. Ricardo notes the concerns and also the fact even in fully sprinklered building AHJ may allow no sprinklers in high voltage switch room.

As far as the original question I am not aware of any statistics and too many variables. Proper design and maintenance of the detection system has an impact. Fenwal stick detectors may be better protection against false alarms if dust is a concern.

Single interlock detection should only trip the valve. Unless a sprinkler has fused or there is piping system damage the pipe will fill with water with no discharge. Piping should have supervisory air pressure to monitor integrity. Note the valve will trip with detection so shunt trip (if part of design) will happen which could be disruptive to plant operations so cross zone detection no matter what system a good idea (and typical on clean agent systems).

Chad

11/18/2025 09:36:29 am

"High Voltage"---- is this transmission and distribution or just 480?

If its T&D voltages on at least one side of the transformer, there isn't a good reason to sprinkler that vault, IMO. You aren't going to suppress or extinguish that fire.

In fact, most giant switchgear/electrical rooms (600v or less) are not a good candidate for sprinklering anyway, and I say that as an AHJ advocate for sprinklers.

Assuming its in/under an occupied structure...Build it with 3+ hour walls and install a smoke evac system, . Perhaps use VESDA, at least use spot detection.

Preaction failure data--- I dont know for a fact but its worth asking FM.

Franck

11/18/2025 09:45:24 am

Stats for wet system spurious activation is 1 to 13 000 000 in terms of installed sprinklers
Spurious activation with water delivery on preaction is therefore even less.
But chances to open the preaction valve spuriously (without water discharge) is more important. But no water discharge.

Nick

11/24/2025 11:25:02 pm

The stat for spurious activation is often trotted out, but it's not actually that useful. It's actually the number of heads that fail "spuriously" due to a manufacturing defect or incorrect install. The stat does not include the actual top contenders of activations when there is no fire. If you look through the NFIRS data the other top reasons are a heat source (oven etc), freeze damage, mechanical impact, corrosion, and deliberate tampering (jails/schools/hospitals etc.)

The rate of activations when there is no fire is much higher than 1 in 13 million per head per year. But I agree that a preaction system would cut that lower by a factor of 1000 or more (that's a guess on my part).

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Data for False Activation in Pre-Action Systems?

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