You can use activated carbon.
The best carbon to use is designed for the sewage industry as it is impregnated with a chemical (non-toxic) that neutralises the hydrogen sulphide and other volatile organic compounds (VOCs) which cause odour. This kind of carbon treats odours in two ways where as non-impregnated activated carbon only traps odours within its pores. I found these guys online who have a phone number you can call if you want to get this kind of activated carbon -
http://www.characterproducts.com.au/product-category/vapour-filtration/
Depending on how much carbon you have and how "dirty" the air is, the filters can last a couple of years.
If you don't want to source the best activated carbon for the job (we got a 25kg bag for about $250+GST which would last you quite a long time if the surplus was stored in an air tight barrel), you can get activated carbon from pool shops and some pet stores, but this carbon isn't ideal for air (you want cylindrical pellet shaped pieces, where as carbon intended for water is more like rough sand). It will work, just not as efficiently as the air won't be able to freely flow between the granules.
The easiest thing to do is to fill a couple of hessian bags with activated carbon and locate them within the enclosure on the substrate. You can hide them in rocks, branches, etc. But the closer to the ground the better as this is where the highest density of the "dirty" air resides. Also they need to be located where air will most likely flow past them such as near the access doors/vents.
If you are handy you can make a box where you mount a small 12v fan which pulls the air from the enclosure into the box and flows over the filtration medium. This is a more efficient means (known as an active flow system where as bags in the enclosure is a passive flow system). The considerations here is that you don't want the fan accessible by your animals because it could hurt them if they touch it or if they deficate on the fan... the expletive quite literally will hit the fan
But if carefully designed, it will do a better job than the bags.
Depending on the size of your enclosure, you will have to experiment with the bag sizes and quantities of bags.