If the salt gets impregnated into organic material, it then becomes a fire hazard. For example, if you spill some Miracle-Mineral-Supplement and wipe it up with a paper towel and set the towel down to dry out. Next if it is warm and you set the paper towel, with the sodium chlorite crystals in it, in concentrated sunlight, it can catch on fire.
I believe you also may be able to set it on fire through impact.
The proper way to clean up a spill is to flush it. If you use a paper towel to wipe it up, make sure you throughly rinse the paper towel out several times before throwing it away.