Road flares ARE classifed as class 1 explosives. They just get a break from the DOT. Check out the MSDS for a road flare:
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While the domestic class is 4.1, the "real" international class is 1.4.
Rocket motors also get a break from the DOT in the form of exemptions:
DOT-E 7887 allows certain 1.4 items to be shipped as 4.1 DOT-E-10996 allows certain 1.3 items to be shipped as 1.4
In order to take advantage of these exemptions you must be listed as a party to the exemption by the DOT.
The thermal stability test (75C) is not a test to see what class something is in. It is a test to see if it is safe to transport. APCP must pass this same 75C test or it is prohibited from transportation in commerce.
The standards for determining a hazard classification are in the United Nations Manual of Tests and Criteria. This is not available (so far as I can tell) online.
I found a DOD versi> It occurs to me that sport rocket APCP is probably safer to ship
than items such as roadway flares or matchbooks (both of which are
> "classified by listing" as "Flammable Solid 4.1" rather than
> "Explosives") - wouldn't APCP meet the thermal stability requirements
> at 49CFR 173.184 for flares ("will not ignite spontaneously or undergo
> marked decomposition when subjected to a temperature of 75 degrees C
> for 48 consecutive hours"), or those at 173.186 for matches (93 degrees
> C for 8 hours)?
>
> These thermal stability tests appear to be considered sufficient to establish
> that the products in question "falls out the bottom" of the "Class 1 Explosives"
> category, without the full test sequences that would otherwise be required for
> materials which fall within the definition of "Explosive" at 173.50 (a). >
> I wonder if there's any way to get a similarly codified exemption for sport
> rocket propellants?
>
> -dave w