Anhydrous Ammonia is nothing to mess around with. This video of an Illinois State Trooper's response to an accident is a cautionary tale for anyone who might come upon an incident in the field.
Remember your first duty is not to add to the casualty list. When you see a tanker or a placard it is time to back-off and evaluate what is going on. Warn others of the hazard and then take what action you can. If you don't have the right equipment, wait for it to arrive. Everyone wants to go home after their shift.