There are filters inside the machines besides the one that keeps dust from being sucked into the unit at the intake.
I think there are some deep inside designed to prevent extremely fine dust / powder from the sieve beds from winding up in the output air line.
I think there is a "bio-filter" that could give you problems in the out put side of the system. They sometimes can get clogged and I think they should get replaced once a year when the oxycon is used for medical reasons but for torch work as long as the air goes through it you don't "have" to change it.
Here is a web site I found a few years back that has documents about servicing hospital equipment;
http://www.frankshospitalworkshop.co...e_manuals.html
See if you can find your model or at least your brand in the list of documents.
You could also contact Salt City Glass. I think I remember seeing maintenance kits for sale there with a package of normal wear items.
Be gentle when you have the covers off because the tubing inside some of the older models can get brittle with time and have been known to crumble or crack with even carful handling.
You can get clear tubing and zip ties from most hardware stores these day if you need to replace any.
At the least take the cover off and make sure you have not got any "guests". Critters love a cubby hole.
These days You Tube should have videos on how to "service" oxycons and they would be worth watching even if they are not your particular model.
The videos that have you take a screwdriver to the parts inside theunit are probably more like "overhauling" than servicing and that you may want to leave to someone more mechanically inclined.
But replacing tubing and zip tying replacement tubing or filters using side cutters or a razor knife is something you should be able to do yourself.
The hardware on these things is built to last for years of continuous use 24/7 and the filters usually get replaced once or twice a year when used 24/7 so with the way we use them for a few hours a day / a few days a week means we can pretty much forget about them all together unless we are working with them out side or in a really dusty environment.
If you get puzzled, take a picture with maybe a pencil pointing to what concerns you and then ask a specific question here or in one of the other threads.
Good luck.
Oh and you probably will need a screw driver to get the case off but not for much of anything else.