Hypoxic Systems

(Paul Clements) #1

Hi All
The NFPA Research Foundation recently published a “Review of oxygen reduction systems for warehouse storage applications”. They followed this up with a webinar (which I attended), which was fronted by some of the authors of the literature review.
This review would be one of the most subjective, unbalanced and incorrect documents are I have ever read, and is a classic example of people not knowing what they do not know. I understand that none of the authors has ever designed a hypoxic fire prevention system, nor have they ever worked in such an environment. To cap it off, they have relied extensively on some fire testing undertaken for FM Global by Zhou and Xin, which uses fire suppression principles to consider a fire prevention system. How do you get a 33 kW fire, complete with excess air, in a hypoxic environment, to suddenly appear in the middle of a rack storage array? If you follow the logic of supplying excess air for the ignition source to its logical conclusion, you will find that the limiting oxygen concentration for all combustible materials is 0%.
I have submitted a critique of the review to NFPA, which covers all of the areas queried by the authors, plus some areas that the authors did not recognise as needing to be considered. To date, apart from acknowledgement of receipt of the critique, I have not had any response from NFPA or the authors.
If any SFPE members would like a copy of the critique, I can supply it.
Paul C.

(Geoff Merryweather) #2

I woudl be interested in reading that. Where is the original NFPA report found?

(Geoff Merryweather) #3

FM did some full scale testing of hypoxic systems in racking. The LOC content is lower than the VdS standard.
The Abstract says

This work evaluated the oxygen reduction system (ORS) for fire prevention in large-scale fire tests. A
two-tier fuel array of standard commodities was set up in a rack storage configuration within an
enclosure. A constant nitrogen/air mixture flow was supplied to the enclosure at a desired oxygen
concentration. The oxygen concentration was varied nominally from 9% to 17%. A premixed propane
ignitor was used as ignition source. The tested materials included five standard commodities of Class 3,
CUP, CEP, UUP and UEP. The impact of the test conditions on fire propagation was examined for Class 3
in detail at different oxygen levels, with the finding that the oxygen concentration is the only major
parameter controlling fire propagation. The results of fire propagation success (Yes or No) were
obtained for the tested commodities under different oxygen concentrations with/without a sustained
igniter to determine the limiting oxygen concentration (LOC) to support fire. These LOCs are generally
lower than the oxygen design concentrations recommended by existing standards including VdS 3527
and EU prEn16750 (Draft).

Assuming that a fire cannot never ever start in a room with combustible is doomed to fail sooner or later.
(edit) my words in the line above got mixed into the quote

(Paul Clements) #4

Hi Geoff
If you Google NFPA RF oxygen reduction systems you will get the RF report, but I will send to you.
Paul C