Richard Cline remarks:

know that there is a CO2 threat from such a heater ...

Not really. But the CO threat can be impressive.

Don't use it in a small tightly
closed area. I only need to run mine for fifteen minutes to get the
chill out of the shop as I don not live in a really cold cllimate.
There are numerous places that leak air into the shop so there is always
a suply of fresh air.

Air leaks are handy. I use two 45,000 Btu Coleman radiant heaters right now,
because I'm too lazy to figurfe out how to hook up my furnace thermostat. I've
got a set of sliding doors that loses a fair amount of air, but not enough on
cold days, which means I need to crack the doors maybe 4" to keep my head
clear. I use a CO detector to make sure.

Charlie Self
"One of the common denominators I have found is that expectations rise above
that which is expected." George W. Bush