Exposure to ammonia gas can cause damage to the skin, eyes and respiratory tract, varying in severity from mild irritation to severe burns and even death. The amount of injury that can occur depends on the amount of exposure to the gas and the concentration of the ammonia levels.
What makes ammonia so harmful is that when ammonia gas is dissolved in water, it becomes extremely corrosive, burning and severely damaging any cells of the body that it comes in contact with.
When the gas comes in contact with the human body, it reacts with the water in the body, transforming into this highly corrosive chemical. If it comes in contact with the eyes, there is a source of water to create this chemical reaction.
When inhaled, the moisture in the lungs provides the moisture and when it comes in contact with the skin, it becomes absorbed into the outer layer, contacting the water within the cells. Lesser ammonia levels will cause less damage and may only result in coughing, eye irritation and a skin rash. High concentrations of ammonia can cause skin to blister, severely damage the lungs and even cause blindness.
Ammonia has such a distinct odour that it’s really hard to miss. At low levels, ammonia is detectable by its unpleasant sharp odour, often present in homes where cat litter boxes are left uncleaned.
By the time ammonia gas has reached high enough concentrations where it is able to do serious damage or even cause death, the smell has become pretty much unbearable. When ammonia odor is powerful enough to cause coughing or burning eyes, it is definitely time to get away from it.
Any time you smell ammonia that is strong enough to burn your eyes and nose, leave the room or building where it is present and go outside to get some fresh air.
More at: http://www.totallyinsulated.co.uk/ammonia-levels.html