I am using PureAire oxygen monitors in my cryogenic test area. The monitor is working great. After the purchase, Bob Jacobson reached out to make sure we are happy with their product, and if we had any question. Installation was very easy. The 4-20 mA output is great for us as we use it for sending text alerts out if oxygen level drops below the safe limit. I would buy again from PureAire if I need more sensors in the future.