Well, Boat Bob, you can clean the soot off by using a Shop Vac with a brush attachment on the hose. That will take off the biggest portion of it. Then you can clean the remainder of the outside with a damp cloth, but be sure to dry the cabinet
afterward. Remove the screws the are holding the face of the of the cabinet on and proceed to clean all of the interior of the heater cabinet fire, with the Shop Vac , being sure to vacuum the burner(s) thoroughly, as well as the pilot assembly and all the
mechanical 's. What soot isn't removed with shop vac, should be removed with a DRY cloth. Then use a can of compressed air with a straw nozzle (like you clean your computer with) to blow out the pilot and all around the pilot assembly.
For the remaining soot on walls, ceilings, furniture, etc. Gently vacuuming is the best way to remove the lion' share of the soot. Then, if necessary, the walls and ceiling can be washed with a diluted solution of Simple Green and water. Clean small areas at a time.
After that, you need to turn your attention, as to why the heater sooted? Several things come to mind ... No annual professional cleaning and service; Incomplete combustion; Vent pipe partially obstructed; Low gas pressure; Clogged burner(s), Obstructed air intake.
If you'd like further information, here is a link to your Owners Manual, which will help you to Troubleshoot the heater.
http://www.empirecomfort.com/EMPIRECOMFORT/pdf2009/manuals/12433-10-0109DV.pdfHope this helped you to answer your questions.