Running generator for 12+ hours?

My last rig had the exhaust tip just just past the outside edge of the body, horizontal. Having the exhaust gases in the rig is more than just a concern. Consider it a literal death trap until corrected. Once you trouble shoot the exhaust, call your local fire dept and ask them to check the rig's interior for carbon monoxide while the genset is running for a while. If they balk at the request (unlikely), ask for the Officer in charge. Please proceed carefully.