NFPA Standard : NFPA standard, Annex C on Enclosure Integrity does not apply to CO2

CO₂ is covered by the NFPA 12 standard which does not have the enclosure integrity test included in it as an appendix nor does it mention testing in that way in the body. Attempts have been made to include it but it has not happened due to a lack of data to support it. Oddly, the equations that are in there have no test data to support them either but have been there for so long that there they stay.

NFPA 2001, which came along many years after NFPA 12, has several inert agents that act similar to CO₂ so our position is that since NFPA 12 is mute with respect to enclosure integrity, then at least 2001 has some kind of procedure to go by. One of the East Coast nuclear power plants spent several hundred thousand dollars showing that the 2001 procedure was a good surrogate for a discharge test and got the NRC to accept it in hearings for their facility because discharging the CO₂ would have grossly affected the integrity of the cabling to the extent that the power plant would have had to have been shut down after a discharge. Cost of shutdown was several million dollars. Their results are proprietary since they paid for the testing that was done at the Factory Mutual Burn Facility on the East coast, which is why they decided not to release them publicly. I was there and witnessed the fact that the enclosure held concentration for a time very consistent with what 2001 would predict.

Ironically, until recently the above mentioned test made CO₂ the only agent that had been verified by actual testing. All the other agents were NOT tested although FM200 and INERGEN went through a battery of tests about 7 years ago that showed the NFPA equation to be fairly close. Recently, we have tested FM-200. Novec 1230, FE125 and INERGEN in the Fike chamber in Blue Springs and verified that they perform inline with the expectations of the NFPA 2001 standard. We plan to discharge CO₂ some time in future but no plan exists with respect to the exact date.

Bottom line is that only 4 of the 10 agents in 2001 have ever been tested to see if the NFPA prediction for enclosure integrity holds true. The rest have just relied upon the density to predict the agent loss rate which has proved to be true for first order affects at least. Therefore, CO₂ predictions using 2001 are merely an extrapolation of what has happened before. Since the agent is so old, it has its own standard which keeps it out of the loop with the more up to date agents. Doing door fan tests on CO₂ protected enclosures certainly makes more practical sense than doing discharge tests for two reasons:

The super cold temperatures( -20C) generated by CO₂ can stress metal and wiring to the extent that they may fail
If the enclosure is extra tight, the CO₂ can damage the enclosure.

Compare this to the chance that the 2001 integrity test may be slightly different from the actual retention time and an excellent case can be made for using the 2001 Integrity test where Retrotec has added the agent density in exactly the same fashion as the other agents. The major manufacturers of CO₂ systems, Chemetron and Fike consult with me regularly on the use of the integrity tests for CO₂ so obviously they feel comfortable with using it and it IS used annually on many Siemens and ABB turbines as well as many other facilities.

Most critical with all these agents is that we must ensure the enclosure is in the window between being tight enough to hold the agent as can be shown with the Annex C Enclosure Test in 2001 and loose enough to prevent the enclosure from being blown apart by the discharge. We are just now collecting data on peak pressures discharge various agent discharges and research shows that the gap between these two leakages is much smaller than we initially imagined making door fan tests an extremely wise part of the acceptance procedure and not something that should be left out just because CO₂ does not appear on the agent list for clean agents. Relying on discharge tests only or no test at all will massively increase risk and costs unnecessarily. Whether discharge tested or not or part of the standard or not, common practice has become to door fan test CO₂ enclosures. Not doing so is not being thorough and not in step with current practice.