When performing spray finishing activities with any product that contains isocyanates (diisocyanates, HDI, MDI, TDI) the minimum respiratory protection to be worn is a powered air supply respirator.

The reasoning is simple: isocyanates DO NOT have good warning properties.

Painters can usually tell when their cartridges are wearing-out, or getting “break through”. However, with isocyanates, the odor threshold is much too high to detect (it can be detected, but only at harmful levels).

In addition, isocyanates have a skin-notation, meaning that if the product gets onto the skin, it can be absorbed. As you can see, this employee was not wearing the proper PPE (personal protective equipment). However, when you’re a consultant, you have temper your comments. We did educate him and also told the general manager of our concerns and the reasoning.

On the plus-side, they had a manometer that was used and the employee knew when to change out the filters.  How this simple meter works is this:  A manometer measures the pressure differential between two different areas. In a paint booth it measures the pressure between each side of the air filters for the air coming into the booth. If the pressure gets too high, then the filters are clogged (or built-up). Notice the arrows on the bottom of the gauge to see when to service the filters. When the manometer (in this case) reads above 0.045 either the fan has to work harder, or the air escapes by the filter (in various ways- more information for another time)