Ha!! Now that there is no Ms. around, maybe it's time to put it where it rightfully belongs ;)

That's what I was thinking. Imagine how exciting it would be to have an accidental fuel spill with a glow plug in the room.

Not true anymore.

The ventless units are very good and proven reliable - that said I'd NEVER operate one without good CO detectors. Common sense.

The biggest complaints I've heard are from folks using them in very tightly insulated spaces and ending up with condensation (one of the byproducts of propane combustion is water vapor - more so when the combustion is complete/clean, such as with a ventless unit).

It's proven technology at this point but you need to use common sense too. They're also very, very efficient.

I have a ceiling hung 85,000 BTU NG forced hot air furnace in my 30 x32 garage.
Heats it up in minutes.

Anybody have a recommendation for a heater for a 20x20 ft garage space? Looking for something to raise the temperature from around mid 50's to 70's for times in the winter when I want to work in the garage and not be cold. Don't really want to plumb a gas line in the garage either.

i maintain: non vented gas heaters are a recipe for disaster.
Plain and simple.

The type of heater required is relative to the amount of insulation. If your space is insulated well, including the door, it won't take much. With a sheet metal door, exposed ceiling and bare walls it will require a warehouse style hanging furnace. If it is tight a large space heater will do the trick.

I have a 20x20 detached garage with R25 ceiling,R12 walls and an insulated overhead door. Easily heated with a ceiling hung 30,000 BTU Mr Heater unit. Fan forced exhaust vented thru wall or roof. I use the roof vent as it is cheaper. (B vent like used for a water heater about $ 25, the sidewall vent kit is stainless steel and adds about $200. Unit was about $400 plus I spent about $500 getting gas to the garage (100 ft underground 1" line )
Around here a garage burner must be vented and mounted above 90 inch off the floor so it doesn,t ignite fumes lying at the floor level.
I have been told the infrared units are much more economical than the fan forced warehouse style heater because garages are very leaky structures. Infrared heats the person not the air .
I hate the propane torpedo style units because as mentioned they produce a lot of water vapour when in use.

You want a direct vent unit. In a direct vent unit, the combustion chamber is sealed from the inside of your house, as it draws combustion air from outside the building.