Air Marksman Compressor

I recently purchased an Air Marksman compressor for my PCP rifle. The fill whip comes with an inline filter. It came with about a dozen replacement filters. Just wondering how often I should inspect these filters and change them?. Just filling up a FX Wildcat rifle......... and no big tanks or anything. Are these inline filters for moisture or dirt? Where is the best place to purchase more filters? Thanks
 
BigCat,
Looked up the Air Marksman compressor, the same small inline filter setup came with my hand pump. Uses a "cigarette filter" style cotton insert that will help trap some oil/moisture, but don't expect any miracles. Check after each fill to determine best replacement frequency, some re-use after allowing to dry. Extra filters can be purchased on eBay, just be aware the "cigarette filter" style inserts come in slightly different sizes. I purchased a 4" ($14) inline (cotton) filter on eBay to supplement the smaller one. WM