if your talking about the 6 " roll of flashing material that is made with butyl rubber and sticky covered with thin aluminum ... nope, no smell even when hot. It is really close to the dynamat and fat mat stuff but not quite as thick in butyl, but the aluminum flashing cover is a little bit thicker "for a 6" roll that is." and it needs to be aluminum taped on the seams. That product I have had in a jeep and the catalytic converter got so hot it caught on fire(the converter not the floor covering), no smell other than burned parts under the jeep and melted tennis shoe soles.:mob: from trying to stomp out the file. Now if your talking about the other stuff that is a form of modified asphalt bitumen.. then heck yeah it smells to high heaven when hot. even sealed it seeps through on a hot Florida day don't ask how hard it was getting that crap off in warm weather, I had to wait for a 40 degree day to even start removing it.%!@$%^&.
