Posted: 14 Mar '13

Properties of H2S

H2S is an invisible gas that is odorless at most concentrations, it is extremely toxic, and extremely flammable, it is also slightly heavier than air.

Invisibility, many gases are invisible to us. For example, right now, stop and look around the room. Can you see the 78 % nitrogen, 21% oxygen and 1% other gases like carbon dioxide and argon. It can be very hard to detect something that you cannot see. H2S is invisible like these gases.

Odorlessness, we cannot smell H2S beyond its safe limit. Niosh list the Immediately dangerous to life and health value for H2S at 100ppm. That is the amount at which our sense of smell is overpowered by the gas. We can smell the gas with it characteristic rotten egg smell at limits below 100ppm, however, these will generally not render us unconscious immediately.

H2S is extremely dangerous to our health. There are three main ways it works on our body, first off it is toxic, it will poison your body, and amounts over 100ppm will cause confusion and altered thinking. Secondly it is corrosive. When hydrogen sulphide mixes with moisture on our skin, in our eyes and in our lungs, it begins to form sulfuric acid. The sulfuric acid then begins to “burn” the tissues. The greater the amount, the more severe the effect. Workers exposed to high amounts of H2S who are revived, often has lung damage and reduced lung function. The Third way H2S affects us is that it is a chemical asphyxiant. It works in a way similar to carbon monoxide. When present in the air, and breathed into the lungs, the gas bonds to the hemoglobin in our lungs, and stops oxygen from doing the same. Essentially it blocks our lungs from allowing oxygen into our blood stream. Thereby asphyxiating us.

Canadian Society of Engineering Safety Alberta Construction Safety Association Canadian Safety Standards Training Alliance