Obviously I don't need 40 of 'em (or do I?) So how many do I need, and which type should I get? Also do you have any recommendations, since Kidde and First Alert is (Home Depot) garbage.
Don't discount the Kidde or First Alert as garbage. Any new unit should be fine as they've corrected the issue(s).
As for how many you need and which type to get (assuming this is for residential use):
For type, do an internet search for "fire extinguisher types" but in general, I recommend type ABC since that covers most of what you encounter at home.
As for how many to get, that's kind of up to you based on your home and level of comfort. Things to consider:
- What's your heating source? If you use wood, coal or other source that produces open flames, you may want to have at least one near each source in case something goes wrong (e.g. an ember popping out into the room and starts smoldering or actually catches fire).
- Egress out of your home in the event there is a fire. Can you easily escape from every area of your home if there's a fire? If a room only has one exit door (no easily escape from windows), you may want one in that room in the event you have to fight your way out. Jumping out of a 2nd or 3rd story window may not be your best/safest way out.
- Do you have youngsters, seniors or others that may need help? If there's a fire in the house, you may need to get to them to get them out of the house. This may entail fighting through fire to get to them.
- Do you do things outdoors or in buildings that could generate a fire? This includes anything from burning brush to doing things that could generate sparks/fire (grinding, welding, torches...).
You need to just walk around your place, identify fire risk situations and locations then decide for yourself what the appropriate protection level you need and/or are comfortable with.