The agriculture community has used anhydrous ammonia as a low cost, highly effective nitrogen-based fertilizer for years. It’s prevalence in the farming community makes it easy to sometimes forget that this a dangerous chemical and should be handled with caution and care.
The word, “anhydrous”, means without water. When anhydrous ammonia comes in contact with moisture, the water and ammonia rapidly combine. When injected into the soil the liquid ammonia expands into gas and is readily absorbed into the soil moisture.
Agricultural anhydrous ammonia is compressed into a liquid state that must be stored in specially designed tanks strong enough to withstand internal pressures of at least 250 pounds per square inch. As the outside temperature increases, the temperature of the liquid in the tank increases causing it to expand. When the liquid expands, the vapor pressure in the tank increases. People working with this substance need to be mindful of these changes. The table below notes the difference in pressure with changes in temperature.
Temperature of Ammonia Vapor Pressure
Another concern is that anhydrous ammonia can be used in the manufacture of dangerous illegal drugs such as methamphetamine. Thieves can cause dangerous damage to holding tanks that the farmer may be unaware of. For this reason, there are some precautions that should be taken when it comes to the installing and management of the holding tanks.
A few tips on holding tank safety:
- Keep tanks in well lighted area and if possible within sight of a residence.
- Beware if you find abandoned containers around your storage tanks, particularly small portable propane tanks used for gas grills.
- Other signs might be pieces of rubber hoses, duct tape coolers, inner tubes or foot prints around tank.
- If you suspect a theft has occurred contact law enforcement authorities immediately, leave the area and keep others away until tank can be inspected by qualified personnel.
- Use locking devices for valves if possible.
- Place brightly colored plastic wire ties on valves for quick visual check. If tie is cut or broken the valve has most likely been tampered with
While anhydrous ammonia can be very useful on the farm, mishandling or poor preparation can be disastrous. Anhydrous ammonia that comes in contact with your eyes, skin or mucous membranes will cause rapid and severe burns as it combines with the moisture of your body. If you are accidently exposed to even a small amount of anhydrous ammonia, you should immediately flush the area with fresh clean water for at least 15 minutes, and seek immediate medical attention.
A few safety tips when handling anhydrous ammonia
- Always wear chemical proof goggles, rubber gloves and heavy duty thick clothing.
- A full face respirator is best, it will provide eye and lung protection
- Tanks should only be filled to 85% to allow for liquid expansion during warm weather
- Keep five gallons of water near tank being filled and another five gallons of water on tractor.
- Individuals should also carry and eight ounce eye wash plastic bottle in case of accidental exposure.
- Inspect all valves and hoses for damage replace or repair if necessary.
- Review safety procedures with all farm workers.