They work fine outside but you have to an have an air source, and they will cut rusted metal but it does tend to eat up the tips faster. I would say that they are definitely the eaisest method for an inexperienced person to cut metal with and they will cut anything. The thicker the metal is, the better you have to be to get a nice cut though. Don't bother with the 110 units, you won't be happy. I hate to say it, but for the money, the chinese units from ebay are pretty good for around the house. You can pick them up in $4-500 range compared to the $1600 I paid for my Hypertherm, and my cousin is a Hypertherm dealer so that was under cost.