Date:         Sun, 05 Nov 95 10:02:33 mdt
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         jonesl@tcplink.nrel.gov
Subject:      Tundra Toaster Heater and Propane Safety II

     I just got thru taking care of a backlog of work that had accumulated 
     and found time to catch up on reading my E-mail.  So - - sorry for not 
     being more timely with this comment.
     
     I have read several postings re Tundra Toaster Heater on the last 3 or 
     4 digests - and would like to make a few suggestions.  I'm the guy who 
     posted on "Propane Safety" a few weeks ago.  My comments are based on 
     over 15 years of professional experience dealing with propane, natural 
     gas, combustion efficiency, RV heater applications, etc. etc.  I have 
     observed and investigated numerous gas explosions, CO poisoning 
     incidents, etc.  So - - - here goes.
     
     First, I don't mean to denigrate the original poster or anyone else.  
     Everybody is looking for an easy, not-too-expensive way to stay warm 
     in a VW camper.    But - - -
     
     The Tundra Toaster Heater sounds like an adaptation of the "100% 
     efficient" unvented make-up air heaters that are use in industrial, 
     commercial, and other applications where there is a high fresh air 
     make-up rate.  These heaters simply burn natural gas or propane right 
     in the make-up air stream to heat the air.  Places that do a lot of 
     painting or other work with volatile chemicals use these all the time  
     
     - - - HOWEVER - - - -
     
     they ALWAYS have plenty of exhaust fans pulling the "used" air out of 
     the enclosed space - and the volume being heated is usually very 
     large.  The amount of air consumed burning the fuel is very small and 
     there is a huge amount of "excess air" - so that the propensity for 
     forming Carbon Monoxide in the combustions products is very low.  
     These applications also have a variety of interlockeded safety devices 
     - so that if the exhaust or the make-up air flow is reduced or 
     interrupted, the fuel safety valve shuts off the fire.             
     
     Now let's consider the use of one of these in a VW camper or other RV:
     
        1)  We're talking about a very small volume of space compared to a  
            factory setting.  Easy to develop big problem quickly.
     
        2)  There is a need to move a fairly large amount of air, but the   
            power reliability (coming from an RV battery) is very          
            questionable - Air flow will undoubtedly fall off as the 
            battery's capactity is used up.  Worse yet - this happens on a 
            rather unpredicable - not necessarily repeatable - basis. 
     
        3)  There are typically only 1 or maybe 2 small unpowered roof      
            vents - not enough to handle a significant amount of air - and 
            a VW van is typically a "tight" enclosure - very nearly air 
            tight with the doors and windows closed.  Unless it's rusted 
            thru all over, we really can't describe VW vans as "well-
            ventilated."   
     
        4)  Most importantly - just like a "free" lunch - There ain't no 
            such thing as "perfect" combustion.  There is always some CO 
            produced  - - and - - as the battery condition drops - and air 
            flow is reduced - there will be more.  CO poisoning is 
            cumulative in the short term.  The rate that CO can enter the 
            blood stream and chemically tie up the hemoglobin's capability 
            to carry O2 to the body's cells is very high - the body's 
            capability to rid itself of CO is very low.  Furthermore, CO is 
            a tasteless, odorless gas - it cannot be detected by humans at 
            concentrations sufficient to kill.
     
     I certainly don't mind these kind of heaters used in well-controlled 
     commercial or industrial applications.  I probably wouldn't mind using 
     one of them in a tent or duck blind - these are naturally well- 
     ventilated.  But I wouldn't expose myself or my family to one of these 
     heaters used in a small, "tight," low power reliability situation.  
     
     We are always looking for a "better" way to do things.  And any time a 
     "new" device comes to our attention we try to use it to solve 
     problems.  But sometimes the ground has been trod before us  -  If 
     these kind of heaters were appropriate for heating campers, they would 
     be readily available at every RV dealer on the continent who was 
     looking to make a few bucks.  And they would have been tested and 
     certified for such use by the UL, the CGA, or other testing 
     authorities.  The fact that they haven't been says someting.        
     
     Better to bundle up in a few more blankets than to wake up dead in the 
     morning.  Better yet - add a couple hundred more bucks to the $400 
     that was mentioned and you'll have enough to afford a well-designed, 
     certified, professionally installed, fully vented RV heater.      
     
     BTW - the same advice applies - even more so (In Spades!!)- to so-
     called catalytic or infra-red propane heaters.  These things don't 
     provide their own combustion air and they exhaust 100% of their 
     combustion products directly into the heated space.  In a "tight" 
     space, the quickly use up the available O2 - and start producing CO.   
      
     I would be glad to respond to any questions or comments from anyone.