Hey there! You might want to try posting in r/HVAC I'll leave this up for a few days, but this sub has been getting a bit wide in its scope lately. That said, I watched your video and this sort of failure to ignite is a massive safety issue. I hate to guess. I hate it with a passion. I hate it even more when it's outside of my area of expertise. But similar ignition problems happen in ranges, cooktops, and dryers when air shutters are incorrectly adjusted. From the factory, everything is set up for natural gas (as opposed to LP) but mistakes do happen. if I blow into the unit it will instantly light up. That clearly points to an incorrect fuel/air mix. Too rich. There should be an adjustable shutter just after the orifice. Open it up a bit. You've ruled out pressure and cleanliness; there really isn't much else to these systems. More on reddit.com

They appear safe enough (blue flame usually means it’s outputting little to no CO) and of course install it per the instructions so it’s not at risk of tipping. I doubt whether moisture brought up by the other commenter would be much of an issue (over and above what would be there already in a Midwest winter). That said, whether this is the right heater for your space depends on what you’re wanting to get out of it. Aside from requiring a new gas line, the main consideration is that it’s a convection heater. So, it will heat the space relatively slowly and need to be operating most of the time via a thermostat. Contrast with an electric forced air heater like this one . This would heat the space quickly and be used mainly when you’re in the space. For example, turning it on 15 min before you’re ready to be in there, then letting it cycle on and off to maintain the set temp, then turning it off when you’re done for the day. We have one similar to this in a large garage/ceramics studio and use it in the way I’m describing, and we’ve been very happy with it and don’t have to worry about gas safety. The only downsides of the electric forced air heater are utility cost and noise. I wouldn’t say it’s loud but definitely would be more noticeable that the gas heater. Cost will depend on how big your space is, how often you’re using it and at what temp, and the price of gas in your area (probably cheaper than electricity, but also recognizing that the gas heater may be running more often than the electric one). There are also gas forced air heaters, which may be a good trade off. The other commenter mentioned one and here’s another example . These do require a vent, but that would probably reduce the safety (and moisture) concerns. More on reddit.com

I personally wouldn’t do something gas & non-vented. I know this is probably an unpopular opinion, but I’ve started to care more about what toxic things I’m breathing as I get older. The research about the long term health impacts of poorly vented gas appliances is not good. The research is mostly around stoves, but I can only imagine an unvented heater would be worse. I’d personally try to go for something electric. More on reddit.com

for heating an attached garage, the vent free wall units aren’t really the best match actually. they can run off a 20 lb tank, but the smaller tanks tend to lose pressure on higher btu heaters which is why the manufacturer is suggesting a 100 lb one. Cuz it’s more about performance than won’t work. Also the bigger concern is CO. any unvented propane heater just puts out carbon monoxide and a ton of moisture so a CO detector in the garage (and one near the door to the house) is basically mandatory. youll also need some airflow like even cracking the garage door 6 inches will help. torpedo heaters especially are meant to run with ventilation. And the inokraft type forced air heaters usually make the most sense for garage use. they heat fast and work fine with a 20 lb tank. they’re noisy tho but they do the job safely as long as you ventilate and monitor CO. for a totally closed garage, a vented gas unit or a 240v electric heater is the safer long term option. but for warming up a workspace on project days, the portable forced air propane heater is generally the easier and more practical route. More on reddit.com