I was flying on a confined space, doing some boilers inspection. The space is 250 feet tall and 12 feet diameter. Everything was going good great, when about 70 feet, there was a sensor sticking out, even with the prop guards it touched the propellers. My heart stopped, and in half a second, decided to try and catch it, I was lucky to save the machine even I got some scratches, but the prop guards took most of the impact on the hands. Broke 3 of the 4. Luckily, is OK. But I don't think Im getting my bird back on that situation. I'm getting new props, and calibrate all sensors, just to be safe.