My understanding is that the fan can be disconnected periodically for things like recording sessions. The fan is there to help the tubes last longer, not to keep them from bursting into flames.
I'm sure others will be happy to either correct me or support me on this.
Customer support is cooperative in providing fan replacement kits too. I did this with my Renegade 212 and the fan is quieter now. Can't even hear it running on stage (when everything is quiet) but I can in my practice room.
Tell your customer the direct out feature on these amps is awesome. I think it sounds better than micing.
Regardless, he has some options.
Good luck.