While the ammonium ion NH4+ has a chemistry similar to that of sodium and potassium ions this is only true in acid solutions. Thus a salt like ammonium chloride is stable in acid solution but begins to liberate ammonia gas when the pH of the solution gets above 7. When heated the solid dissociates into ammopnia gas and hydrogen chloride. Ammonium bicarbonate is used as a leavening agent beause it decomposes to ammonia, water and carbon dioxide at oven temperatures. Ammonium carbonate is so unstable that it does not exist at all. Solid ammonium thiosulfate slowly releases ammonia even at room temperature. As Ian points out it is also deliquescent absorbing water from the air and liquifying. This is why it is sold as a solution of known composition.
Speaking about booms, ammonium nitrate makes an excellent explosive and will detonate spontaneously if a large quantity is allowed to become moist. This happened in Texas City in 1947 when a whole shipload (2300 tons) went up taking most of the town with it. At least 581 people were killed.
I never buy anything from PF as I think their prices are too high and the purity of some their chemicals suspect. I buy developing agents and some other chemicals from www.techcheminc.com.