Is this iso booth safe?

Hi, I'm planning to build this iso booth I found on the web ( http://www.amptone.com/diyisobox.htm )for recording my Fender Hot Rod Deluxe amp in my apartment. As you see from the pics, this one was made for a cabinet only. Is is safe to use a combo inside it? I mean, with the heat, valves and all. I do not want to start a fire or damage my amp. Also, about the sound quality, is it possible to get a nice sound inside such a small booth? Thanks!

you might need to add some air exchange to keep the box cool.