Matching the theoretical to reality provides the piece of mind for fire suppression and environment stability.
Once a Server room/Data Centre is built, the ever so critical contents seem to be forever evolving and growing, with the needs of the business but the building envelope stays the same, and along the way it also picks up new and “amazing or perhaps horrendous” holes created by trades or tech staff.
The one thing that doesn’t seem to get much attention within a computer room is the building fabric/building envelope and its ability to contain and suppress a fire while at the same time, ensuring key environmental stability, that assists hardware longevity and low energy costs for controlling humidity and temperature.
Before we move onto more detail, it’s imperative that we explain two important things that all Data Centre/Server Room operators should have a basic understand of;
1). There are two primary forms of fire suppression, forget about the type of gas used (FM200, Novec or IG-55), fire suppression systems can operate in 2 standard distinct forms:
- Continuous mixing – With air conditioners in operation
- Fire suppressant gas will circulate and be pushed out where ever holes and high pressures exist
- Descending interface – With air conditioners not in operation
- Fire suppressant gases are heavier than air, so they will gradually leak through holes low lying.
2). Secondly, it’s important you know what a baseline/bias pressure is in a room that has a fire suppression system. Bias pressure is the normal everyday pressure acting in a room depending on what pressures are in the building from HVAC or outside wind pressures, and how well those pressures are exposed, to the room that is being tested.
The single most important point of failure that can compromise a fire suppression system and energy efficiency/humidity & temperature lies in the building envelope under false floor plenums or ductwork that distributes air to and from air handlers. Areas, where elevated pressures up to 10 Pascal’s exist to keep equipment at an optimum temperature, must be almost entirely air tight. Air tightness is extremely critical for both Continuous Mixing and Descending interface but for different reasons, no matter what agent is being used. The leakage you are specifically looking for is located under walls or through walls, particularly when hundreds of cables have been pulled through a wall.
Things to focus on in-house:
- Testing on whether air conditioners shut down or stay running should be thoroughly tested and reported on, what does the documentation say and
- Check the state of all penetrations under the false floor or your return air plenum. Resolve any penetrations that are evident. Under floor air tightness is critical for fire and energy efficiency, so make it perfect.
- It is excellent practice, which no matter whether a room is descending interface or not, it should be reported what the bias/baseline pressure is in a computer room during normal operation because it will give you clues of potential issues in the room. Even though a computer room might pass an integrity room test when everything is turned off, high operating bias pressures is unacceptable for a continuous mixing fire suppression system, but it could also indicate considerable lower leakage under a false floor, which is not desirable for both descending interface and continuous mixing fire suppression system.
- If a computer room manages to become quite air tight, it then needs to be understood, whether a computer room has or requires a relief vent. This is critical because walls can be damaged in the event of an incident. When a fire suppression system goes off, depending on the airtightness of the building envelope, momentary pressures can go up to 1000Pa. Some agents cause more negative pressure and the peak pressure is related to “leakage to Volume” ratio. Seek professional advice.
- Does the room behave, as it should in the event of a triggered fire suppression system?
- Do extraction fans turn off and also damper?
- Do dampers to the Building HVAC system close?
- Does the Pressure relief vent work complimentary to your gas fire suppression system?
To ensure your data center is prepared for an incident while also improving the performance of your computer room, do the following:
- Inspect religiously new works that occur to your computer room about penetrations, especially under a supply false floor plenum, or a return air plenum. Make sure contractors understand what you expect.
- Get your computer room Fire Integrity tested on a yearly basis
- Insist on a bias/baseline pressure measurement during normal computer room operation, and if possible, a baseline with everything turned off (necessary with a descending interface installation). Don’t accept a report which says 0 Pascal’s. All computer rooms have some bias pressure, and it may very well be close to zero Pascals. For example -.17Pa gives you confidence an actual measurement was taken.
Currently hot/cold aisle Containment solutions are quite popular. These solutions can do wonders, but it’s important to ensure you don’t lose site of the big picture when retrofitting these types of solutions into computer rooms. Make sure you consult your fire integrity consultant before moving forward with a containment solution.
Think of integrity room testing as a means of understanding air tightness/energy efficiency as well as protecting your equipment and you will get more out of the whole exercise.
Keep your eye on the computer room baseline/bias pressure. It’s a number that says a lot.
By John Konstantakopoulos