Careful with that. The MSD for my can of Prestone Starting Fluid says: 40-70% ethyl ether, 25-40% heptane (a hydrocarbon) and the balance is CO2. So, yes, it is not 100% ethyl ether, but a whopping amount is.
My point was just that the ether injection system delivers a metered dose that is deemed safer for the engine than a handheld spray.
The flame heater, when fully operational, works well. It has several failure-prone parts and does not age gracefully.
We have had sub-freezing temperatures here for the last few nights. I started my truck this morning (with brand new 1000CCA batteries, mind you) and she started after about 5 seconds of cranking. No flame heater or ether start needed.
I know that when it dips to -15 or -20 Celsius, she does not want to fire without ether, unless you do not care about excessive cranking.