Your internal wood burner will be surrounded by a fence to help prevent contact with the hot surfaces inclduing chimney and once the fire is lit you should not make any contact with the boiler. We highly recommend to purchase the chimney heat guard if you have some children around or potentially adults after few drinks. No surface underwater will be hot enough to cause a burn unless sustained contact is maintained.

External heater is surrounded by water and the wall are contantly cooled down however the chimney and the door will be hot.