Be sure to know what you are doing. Don't let the wind blow the powder in your eyes or let the powder come in contact with water. Apparently the powder reacts with water and gets HOT, hot enough to cause burns. It does not cause burns when in contact with blood. The Tactical Med section at the Lightfighter Forum has a thread going for more details.
The stuff does work, but do some research first. It comes in 3 small envelopes or 1 large. The 3 small should be fine for non "battle" uses.
Dave