General Information on Hazardous Gases

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(I) Carbon Monoxide

Carbon monoxide, with the chemical formula CO is a toxic, flammable, odorless, colorless and tasteless gas. It is slightly lighter than air (28.0101 g/mol). It is produced by the incomplete combustion of carbon-containing fuels such as coal, wood, charcoal, natural gas, and fuel oil.

Carbon monoxide interferes with the distribution of oxygen in the blood.  Depending on the amount inhaled, this gas can impede coordination, worsen cardiovascular conditions, and produce fatigue, headache, weakness, confusion, disorientation, nausea, and dizziness. Very high levels can cause death. It is often being called "the silent killer". Figure 1 below shows the effect of carbon monoxide on human beings.

(II) Hydrogen

Hydrogen (H₂) is a colorless, odorless, tasteless, highly flammable diatomic gas. Many reactions may cause fire or explosion. Its relative density, compared with that of the air, is 0.0695. Hydrogen is the most flammable of all known substances.

Hydrogen gas in highly flammable and will burn at concentrations as low as 4% H2 in air. It combusts according to the following balanced equation:

2 H₂ + O₂ → 2H₂O + 572 kJ

When mixed with oxygen across wide range of prorions, hydrogen explodes upon ignition. Hydrogen burns vialently in air. Pure hydrogen-oxygen flames are nearly invisible to the naked eye.

(III) Methane

Methane (CH₄) is most commonly known as Natural Gas. Methane is odorless and lighter than air. It tends to rise and accumulate near the higher, stagnant parts of enclosed buildings. The main hazard is its flammable, explosive nature. Methane can explode at concentrations of 50,000 ppm or more (a level of 5%).

Methane can displace oxygen in confined areas, resulting in an oxygen-deficient atmosphere. Methane can explode at concentrations of 50,000 ppm or more (a level of 5 per cent).

The Occupational Safety and Health Administration (OSHA) has no permissible exposure limit for methane, but the National Institute for Occupational Safety and Health's (NIOSH) maximum recommended safe methane concentration for workers during an 8-hour period is 1,000 ppm (0.1 percent). Methane is considered an asphyxiant at extremely high concentrations (500,000 ppm) and can displace oxygen in the blood.
 

(IV) Propane

Propane (C₃H₈) is heavier than air (1.5 times denser). In its raw state, propone (sometimes is called LPG or LP-gas) is an odorless and colorless gas. Propane is flammable when mixed with air (oxygen).  The fact that it has a tendency to stay low to the ground means there's more potential for propane to be ignited and cause an explosion.

While propane is used as a gas for fueling appliances, it is transported and stored as a liquid under high pressure in specially designed containers referred to either as tanks or cylinders. When propane changes into gas vapor, it expands in volume by about 270 times, meaning that propane is very economical to store and transport as a liquid rather than as a gas vapor. However, this characteristic also means that even a small leak of liquid propane can result in much larger quantity of propane vapor, which can be especially dangerous in a confined space.

Similar to any other flammable gas or flammable liquid, propane is very safe when stored and handled properly. However, if propane is not properly and safely stored and handled, it can cause property damage, injuries, or even death. For this reason, it is important for the safety of the members of your household that they have a thorough understanding of the properties and characteristics of propane, and the hazards and risks associated with its use.

(V) Hydrogen Sulfide

Hydrogen Sulfide (H2S) is a by-product of oil and gas production operations. It is contained within gas or crude oil underground. When a well that produces oil or gas contains hydrogen sulfide, it is call a sour well, when it doesn't it is called a sweet well.

Hydrogen sulfide is also released during the decaying of organic materials such as in sewage treatment plants.

It is a toxic gas that is extremely poisonous in very small quantities. Although the odor can be detected at a very low concentration, the sense of smell is lost in just a few minutes after exposure, due to olfactory fatigue. This makes it impossible to sense dangerous concentrations.

Inhaling H2S at a few hundred ppm may result in acute poisoning, and although the gas is an irritant, the systemic effects from absorption of H2S in the blood stream overshadow the irritant effects.

When the amount of gas absorbed by the blood exceeds that which is readily oxidized, systemic poisoning results, with a general action on the nervous system. Within seconds and without warning unconsciousness and collapse can occur. For that reason many persons have lost their lives attempting to save a victim who has collapsed from exposure.

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