Sentence:  Take care when handling <WSD>primers</WSD>, especially ensure that your fingers are free of oil or dirt. Oil can affect the detonating properties of the <WSD>primer</WSD> pellet, and can be the cause of misfires if too much oil gets into the <WSD>primer</WSD>. 
Meaning of the word marked with <WSD> tags:  Any substance or device, such as priming wire or blasting cap, used to ignite gunpowder or other explosive.