Since the items are used on a recurring basis to reduce income, they are considered assets. Normally, assets used in the production of income are capitalized and depreciated over time. However, there is a safe harbor rule that very well may apply for you, that will allow you to just deduct the costs as an expense and be done with it.
Since the items are not a physical and permanent part of the structure, if you paid less than $2,500 for the assets then you can just expense them and be done with it forever.
