I think the key is to keep them cool & dry. Always keep mine in the cellar with de-humidifier running (in summer months). Humdity stays around 50% of lower & have never had a problem. I don't know how many primers or how much powder I have as it varies, but it's not uncommone to have 10-15K pimers or over 20lbs. of powder at a given time. I am sure this is a small amount compared to many folks here. Local fire chief knows about all this as I load his '06 shells for him! Any fireman will realize that the fire/explosion danger is much more likely in your garage where you keep the 5 gal. can of gas for lawn mower, the spare 20lb. tank of propane for gas grill, etc. Common sense says keep any type of heat source, spark or flame away from primers and/or powder & the chances of anything bad happening are very, very minimal.