Facility Safety Management

FM says that Sensidyne’s low PPM gas detector for ammonia has passed both performance tests and can be used in hazardous locations, such as:

• Meat, poultry, and fish processing facilities;
• Dairy and ice cream plants;
• Wineries and breweries;
• Fruit juice, vegetable juice and soft drink processing facilities;
• Cold storage warehouses;
• Other food processing facilities; and
• Seafood processing facilities aboard ships, and petrochemical facilities.

When mixed with lubricating oils, ammonia’s flammable concentration range is increased. It can explode if released in an enclosed space with a source of ignition present, or if a vessel containing anhydrous ammonia is exposed to fire.

OSHA says ammonia is not, strictly speaking, a poison and repeated exposure to it produces no additive (chronic) effects on the human body. However, even in small concentrations in the air it can be extremely irritating to the eyes, throat, and breathing passages.

Anhydrous ammonia is easily absorbed by water. At 68º F, about 700 volumes of vapor can be dissolved in one volume of water to make a solution containing 34 percent ammonia by weight. Ammonia in water solution is called aqua ammonia or ammonium hydroxide.

Ammonia, especially in the presence of moisture, reacts with and corrodes copper, zinc and many alloys. Only iron, steel, certain rubbers and plastics, and specific nonferrous alloys resistant to ammonia should be used for fabrications of anhydrous ammonia containers, fittings and piping.

Ammonia will combine with mercury to form a fulminate, which is an unstable explosive compound.

Anhydrous ammonia is classified by the Department of Transportation as nonflammable. However, ammonia vapor in high concentrations (16 to 25 percent by weight in air) will burn. It is unlikely that such concentrations will occur except in confined spaces or in the proximity of large spills. The fire hazard from ammonia is increased by the presence of oil or other combustible materials.

Anhydrous ammonia is an alkali, and primarily affects three areas of the body:

• Eyes;
• Lungs; and
• Skin.

Eyes

Everything from mild irritation to destruction of the eye can occur depending on whether a spray or gas is involved. Ammonia penetrates the eye more rapidly than other alkalis.

Skin damage depends upon the length and concentration of exposure and can range from mild irritation, to a darkened freeze-dry burn, to tissue destruction.

Because liquid ammonia boils at -28º F, the expanding gas has the potential to freeze anything in its path of release, including human flesh and organs.

Because water can absorb ammonia so readily, it is a factor that contributes to human toxicity. Ammonia will keep spreading across contacted skin until the chemical is diluted by skin moisture.

Alkalis effect tissue differently than acids, which tend to burn and seal off a wound. Alkalis, such as ammonia cause liquidization of tissue and turn tissue into a sticky “goo” and mix with this tissue, causing further damage. As a result, anhydrous ammonia burns keep spreading until the chemical is diluted.

In addition to liquidization, supercooled anhydrous ammonia spray causes a freeze dry effect like frost bite when it hits the skin.

The spray is also capable of freezing clothing to skin so that if the clothing is removed incorrectly whole sections of skin can be torn off.

High concentrations in the air can also dissolve in the moisture of the skin or perspiration and result in a corrosive action on the skin and mucous membranes.

• First, flush the eyes with clean water. Then flush the whole body or the exposed area with generous amounts of water; includes the hair, ears, under chin, and armpits. Any water source is acceptable; such as showers, hoses, or stock tanks.

• Remove contaminated clothing, but only after careful flushing and warming to prevent the previously mentioned problem of skin sticking to the clothing.

Anhydrous ammonia is a clear liquid. In refrigeration systems, the liquid is stored in closed containers under pressure. When the pressure is released, the liquid evaporates rapidly, generally forming an invisible vapor or gas.

The rapid evaporation causes the temperature of the liquid to drop until it reaches the normal boiling point of -28º F, a similar effect occurs when water evaporates off the skin, thus cooling it. This is why ammonia is used in refrigeration systems.

Liquid anhydrous ammonia weighs less than water. About eight gallons of ammonia weighs the same as five gallons of water.

Liquid and gas ammonia expand and contract with changes in pressure and temperature.

For example, if liquid anhydrous ammonia is in a partially ﬁlled, closed container it is heated from 0º F to 68º F, the volume of the liquid will increase by about 10 percent. If the tank is 90 percent full at 0º F, it will become 99 percent full at 68º F. At the same time, the pressure in the container will increase from 16 pounds per square inch (psi) to 110 psi.

Liquid ammonia will expand by 850 times when evaporating: Anhydrous ammonia gas is considerably lighter than air and will rise in dry air. However, because of ammonia’s tremendous affinity for water, it reacts immediately with the humidity in the air and may remain close to the ground. FSM