The problem is that liquid flammability is highly dependent on the test conditions used to measure it.
A fluid that is very difficult to ignite as a liquid pool by briefly exposing it to a naked flame can burn vigorously if in the form of a fine spray mist.
For that rule to have any value, it will need to specify how they are to determine if the coolant is flammable.
1. do you depend on the MSDS sheet NFPA rating for the undiluted coolant?
2. is there a field test they will accept to demonstrate it is not flammable?
Each product should include in the MSDS sheet an NFPA 704 Hazard Identification ratings system rating.
What do the numbers and symbols on an NFPA fire diamond mean?
The diamond is broken into four sections. Numbers in the three colored sections range from 0 (least severe hazard) to 4 (most severe hazard). The fourth (white) section is left blank and is used only to denote special fire fighting measures/hazards.
For the flammability ratings the numbers correspond to:
4 Will rapidly or completely vaporize at normal pressure and temperature, or is readily dispersed in air and will burn readily.
3 Liquids and solids that can be ignited under almost all ambient conditions.
2 Must be moderately heated or exposed to relatively high temperature before ignition can occur.
1 Must be preheated before ignition can occur.
0 Materials that will not burn.
Which threshold does SCTA consider "flammable" for the purposes of their ruling?
Likewise as you mention when diluted with water, normally flammable liquids lose much of their ability to ignite, but even at high dilutions, if exposed to heat long enough to drive off the water as in a mist exposed to naked flame, you are back to the flammability of the undiluted material. Common windshield washing liquid is an example, it is very difficult to ignite as it comes out of the bottle but if introduced to a well developed fire it will burn off the alcohol portion of the liquid as the spray evaporates.
Ethylene glycol has a flash point of 232 deg F so if preheated to that temp it becomes flammable in the context of an escaping spray of coolant into an engine fire environment.
Flash points are determined experimentally by heating the liquid in a container and then introducing a small flame just above the liquid surface. The temperature at which there is a flash/ignition is recorded as the flash point.
Two general methods are called closed-cup and open-cup. The closed-cup method prevents vapors from escaping and therefore usually results in a flash point that is a few degrees lower than in an open cup. Because the two methods give different results, one must always list the testing method when listing the flash point. Example: 110 oC (closed cup).
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OSHA's 29 CFR 1910.106 standard discusses the methods in some detail:
(a)(14) "Flash point" means the minimum temperature at which a liquid gives off vapor within a test vessel in sufficient concentration to form an ignitable mixture with air near the surface of the liquid, and shall be determined as follows:
(a)(14)(i) For a liquid which has a viscosity of less than 45 SUS at 100 deg. F. (37.8 deg. C.), does not contain suspended solids, and does not have a tendency to form a surface film while under test, the procedure specified in the Standard Method of Test for Flash point by Tag Closed Tester (ASTM D-56-70), which is incorporated by reference as specified in Sec. 1910.6, shall be used.
(a)(14)(ii) For a liquid which has a viscosity of 45 SUS or more at 100 deg. F. (37.8 deg. C.), or contains suspended solids, or has a tendency to form a surface film while under test, the Standard Method of Test for Flash point by Pensky-Martens Closed Tester (ASTM D-93-71) shall be used, except that the methods specified in Note 1 to section 1.1 of ASTM D-93-71 may be used for the respective materials specified in the Note. The preceding ASTM standards are incorporated by reference as specified in Sec. 1910.6.
(a)(14)(iii) For a liquid that is a mixture of compounds that have different volatilities and flash points, its flash point shall be determined by using the procedure specified in paragraph (a)(14) (i) or (ii) of this section on the liquid in the form it is shipped. If the flash point, as determined by this test, is 100 deg. F. (37.8 deg. C.) or higher, an additional flash point determination shall be run on a sample of the liquid evaporated to 90 percent of its original volume, and the lower value of the two tests shall be considered the flash point of the material.
(a)(14)(iv) Organic peroxides, which undergo auto accelerating thermal decomposition, are excluded from any of the flash point determination methods specified in this subparagraph.
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I suspect the best option would be to use only water, or possibly water + water wetter.
That of course raises issues of preventing freezing during cold desert nights. You might want to bring an old blanket to toss over the radiator/hood at night to minimize radiant cooling and risk of freezing if there is a brisk night. Or you could install a block heater and warm the block just before you leave the salt for the night.
MSDS sheet for water wetter --- flash point >300 deg F
http://www.redlineoil.com.au/Uploads/Downloads/MSDS%20WaterWetter%20Euro%207_01.pdfMSDS sheet for ethylene glycol --- flash point 231.8 deg F
autoignition temperature 748.4 deg F
http://www.sciencelab.com/xMSDS-Ethylene_glycol-9927167MSDS sheet for Evans NPG --- flash point 225 deg F
http://www.evanscooling.com/download/Evans%20MSDS%20NPG.pdfAll three of the above have an NFPA flammability rating of 1
Larry