To answer your first question, there is no code which prohibits the use of a clean agent. The building codes may require some type of fire suppression, typically fire sprinklers. They may also require some method of fire detection. How either of these two (2) components are installed can be found in one or several NFPA Standards.
Both names you've mentioned are "Trade Marked", and the associated names referenced in NFPA 2001, are HFC-227ea, and FK-5-1-12 respectively. Tyco Markets Novec as "Sapphire" under the Ansul brand, and "NOVEC 1230" under their PyroChem brand. UTC Companies market it simply as "NOVEC 1230" (Kidde, Fenwal, Chemetron). I only mention this because since the demise of Halon 1301, everyone is trying to position themselves by using various trade names these days.
The NFPA standard for clean agents is NFPA 2001. The standard divides "Clean Agents" into two (2) categories; a) Halocarbon, b) Inert Gas. The two (2) agents you mentioned (both halocarbon agent) will experience thermal decomposition when exposed to fire. The by product is HF Acid. The amount of HF Acid is defendant on a number of issues; a) initial design concentration, b) fire size, c) discharge time.
In the scenario you mentioned, it's more likely that the system will be discharges while the fire is in it's incipient stage, with little or no visible fire. There is plenty of testimonies of these systems successfully extinguishing a fire.
- Design Concentrations
FM-200, the first Halocarbon agent on the market following the demise of Halon 1301, originally had design concentrations above 7% by volume and varied by 1% or 2% depending on the manufacture. For a time there was a dispute in how the concentrations were established and eventually (2002 or 2003 I believe) the design concentrations dropped to 6.25% in you're application. This represents a 20% safety factor over what is defined as the "Extinguishing Concentration". The European standards require a 30% safety factor.
NFPA 2001 does require that the system designer take into considerations the by products of combustion, but doesn't offer clear guidelines as to how high the concentration should be.
In the 1301 Days, system designers had to have a 5% concentration, however most would design to 6%, due primarily to experiences in failed discharge tests where the design concentration failed to be retained for a given period of time. Now a days, NFPA 2001 requires "Room Integrity Testing" or "Door Fan" testing to insure that the protected space is sufficiently air tight to retain the concentration. As the current market is so competitive, you'll not find a system designer using a higher concentration than required by Codes, unless it's required by a project spec.
- Fire Size
There have been numerous tests conducted by NIST, USCG, and Hughes Associates, to understand the by products of combustion. Some manufactures of Inert Gas systems used the HF Acid by product as a marketing strategy for their product. Some of the fire tests produced very large quantities of HF Acid but the fire size was considered to be unrealistic in most cases. Testing by Hughes Associates demonstrated that the typical fire in a data processing center netted very little HF Acid. (see NFPA 2001, 2008 edition, Appendix A, Section A.5.7.2).
- Discharge Time
Halocarbon agents, like Halon 1301, are required to discharge 95% of the required agent, in 10 seconds to minimize the potential of HF Acid due to thermal decomposition. Because Inert Gas agents don't experience thermal decomposition, they're permitted to have a 60 second discharge.
A number of years ago, Tyco and Great Lakes got into a heated battle, which all started due to an advertisement slogan by Great Lakes "When You don't Have a Minute to Spare". Tyco responded with a side by side comparison of a live fire discharge test and used the slogan "...The Shortest Minute...". The video demonstrated several things there which is what brought about the mud slinging...
a) The FM-200 system discharge in 10 seconds, but the fire didn't appear to be extinguished for some 59 or 60 seconds later.
b) The Inert Gas system discharged in 60 seconds, and the fire appeared to be extinguished in the same amount of time as with FM-200, maybe even a second sooner.
c) Visibility in the FM-200 space was noticeably reduced.
After several years the two agreed to disagree, and the law suit stopped. Tyco pulled the video from the market and remade the video using only their agent and titled the add "Still the shortest minute"
There are really only two (2) things an end user should consider when selecting a clean agent systems; a) feasibility of pressure relief venting for Inert gas agents, b) cost of recharge for either agent.
- Pressure Relief Venting
Rooms or buildings which are stand alone will have marginal cost for venting. If the room is centered within a larger building the venting will have a higher cost. Most system providers won't be able to quote the cost of this venting as it's usually a HVAC contractor with the tools to install them.
- Cost of Recharge
The cost to recharge a FM-200 system will be close to $0.85 per cubic foot of protected space. For an Inert system it will be closer to $0.26 per cubic foot of protected space. I've yet to see a halocarbon agent come close, in terms of cost, to that of an Inert agent, when the cost of the recharge is taken into consideration.
Regards,
Dan Marr
"Real world Knowledge isn't dropped from a parachute in the sky but rather acquired in tiny increments from a variety of sources including panic and curiosity."
