There are a couple of safety-related features that you should keep in mind when buying any kind of electrical heater to warm up your shop or garage. of course, these features will somewhat be dependent on the kind of heater that you end up getting.   The first feature, one that all should have, regardless of what type of electrical heater it is, is overheat protection. You want to make sure that your heater can detect when it is overheating, usually due to the blowers on the heater being blocked by something. If you accidentally drop a shop towel or a tarp in front of the blowers of an electrical heater, it needs to know if the heat isn't escaping, otherwise, it will build up inside of the device and cause all sorts of issues frying the internal electronics. Proper heating devices will have sensors that detect this type of overheating and can trigger an automatic shutoff. They will usually have an error code displayed somewhere so that you can check the owner's manual and see what the cause is. Usually, it is often just a blockage in or in front of the blowers of the heater.   The other major safety-related feature that some electric heaters should have is a sensor that triggers an automatic shut off when the device is tipped over. While many devices don't need this because they are wall devices that are permanently installed, any free standing devices should have this featured included. Let's say you are moving something around in your shop or just pulling on a large extension power cord when using a power tool. If the free standing heater gets knocked over because of this, it can cause some serious internal damage if the heater continues to run while tipped over.