I done this job for 32+ years, first 12 for the RAF, the rest on commercial, business, VIP and VVIP jets. I wouldn't spray polyurethane paints with an air fed half mask at all, you eyes are great organs for absorbing what's in the air, isocyanates, volatile organic compounds, to mention just a couple there. It specifically states on the technical data sheet, TDS, that appliers of polyurethane paints MUST wear a FULL Face airfed mask.