Filters

Does anyone know if there is a schematic showing where the cabin filter is on a 21 international LT? I found and replaced the filters in bunk and the one outside on the firewall(I was told that one was the fresh air filter) but can't find the in cab one for up front. I pulled off the panel under the fuse array and found the blower but didn't see anything that looked like a filter housing. I asked a tech at Speedco and he got no results for air filter for this model. I know that can't be right.
Main issue is, I haul carbon black. I made the mistake of not having gloves or a baggy when I replaced the bunk filter. That was nasty, so I am thinking the one in front is going to be just as bad.