Kodak states it to be 17 or fine. Infrared red film has an additional layer that has a dye added to it, making that layer sensitive to IR radiation. This fourth layer is in addition to the already normal 3 layers that are sensitive to blue, green, and red light. These layers are then sensitive to reflective light. Some objects reflect infrared radiation and some absorb it.
Water absorbs infrared radiation and beach scenes show that.
Human flesh, foliage and other things reflect it. On the print it turned out grey. I was surprised. This additional layer is why filters are used. Filters pass some light and absorb others.