what type face mask

With isocyanates you also need to protect your eyes as the isos are absorbed by the moisture in your eyes. That would make the full-face mask or the hood the preferable arrangements. If you need to wear eyeglasses during painting, the full-face mask makes that difficult, if not impossible. For eyeglass wearers, the hood would be the best arrangement. As far as air supply goes, it needs to be breathable air, obviously. If supplied by compressors, they should be oil-free and tankless. The same goes for low pressure blowers. Either compressors or blowers need to be of a capacity and operating pressure sufficient to supply a continuous flow of air to the facepiece or hood through whatever hose connects the two. Four cfm is the standard for a facepiece and six cfm is the standard for a hood. The source of air also needs to be located in an area where there is no possibility of harmfull fumes from any source being inducted into the intake and sent to the mask/hood. The best arrangements include not only the mask/hood but also the air source and the connecting hose. Hobby-Air is a common low-cost system. So is the Breathe-Cool product line of supplied-air systems. There are others but they are considerably more expensive.

Rod