CONCENTRATION EFFECTS

EFFECTS

1 ppm

The odour can be detected.   

10 ppm

Working limit for an exposure period of 8 hours. At this level, it is advisable to wear suitable breathing apparatus.   

20 ppm

Maximum limit for exposure at work. No worker should be exposed to 20 ppm at any time.   

100 ppm

Loss of sense of smell within 2-15 minutes. Possible burning sensation in the throat, headache and nausea.  

200 ppm

Sense of smell lost rapidly. Burning of the eyes and throat.  

500 ppm

Confusion and loss of balance. Problems with breathing within 2-15 minutes. Emergency medical aid required.  

700 ppm

Immediate loss of consciousness. Onset of convulsions, loss of sphincter and bladder control. Breathing stops and death ensues if emergency help is not forthcoming.  

1000 ppm

Causes immediate loss of consciousness. Death or permanent brain damage will ensue without rapid emergency intervention.  

GAS

CHARACTERISTICS OF GASES

SO₂

Sulphur dioxide (or sulphur oxide or sulphurous anhydride) is a colourless gas with a characteristic smoky odour, very soluble in water.  The substance acts as an extreme irritant to the eyes and respiratory system. Inhalation can cause pulmonary oedema and prolonged exposure can lead to death. In the presence of water or water vapour, it attacks many metals, such as: aluminium, iron, steel, brass, copper and nickel. In a liquefied state, it can erode plastic and rubber materials.     

Explosive Mixtures:

As the name suggests, these are mixtures of gaseous hydrocarbons produced during natural or chemical/industrial processes which can be inflammable in the presence of oxidisers or sources of combustion. Such a mixture may contain methane, ethane, propane, butane, etc.  

CO

 Carbon monoxide (or carbonous oxide), with the formula CO, is a particularly insidious poisonous gas as it is at the same time odourless, colourless and tasteless. Carbon monoxide   combines with the ferrous ions in the haemoglobin of the blood to form a more stable complex than that formed by oxygen. The creation of this complex, carboxyhemoglobin (COHb), with its allosteric properties, greatly reduces the capacity of the blood to carry oxygen to the tissues. Carbon monoxide poisoning leads to a state of unconsciousness as the brain gradually receives less and less oxygen, and ultimately results in death by asphyxia.        

CO₂

Carbon dioxide (also known as Carbonic oxide) is an acidic oxide (anhydride) formed from one atom of carbonate combined with two atoms of oxygen. Carbon dioxide results from the combustion of an organic compound when there is sufficient oxygen present to complete the oxidation process. 

Carbon dioxide is mainly produced as a consequence of the following processes:

 As a secondary product by plants manufacturing ammonia and hydrogen, where methane is converted into carbon dioxide; 

By the combustion of oil and fossil fuels, mainly by power stations and motor vehicles;                   As a by-product of fermentation;

By the thermal decomposition of CaCO3;

As a by-product in the production of sodium phosphate;                                                                      Directly from underground sources of carbon monoxide.  

Carbon dioxide is a colourless and odourless gas: it is not toxic in itself but can lead to death from asphyxia in high concentrations. Breathing an atmosphere rich in CO2 produces a sour taste in the mouth and a stinging sensation in the nose and throat: this is due to it reacting with water to form carbonic acid. The density of carbon dioxide at ambient temperature and pressure is approximately one-and-a-half times that of air; it therefore tends to accumulate near the bottom of closed, unventilated spaces.  

VOC

The acronym stands for Volatile Organic Compounds, and the term is used to include various groups with differing physical and chemical behaviour. Within this classification are both hydrocarbons containing carbon and hydrogen as single elements (alkenes and aromatic compounds) and compounds which contain oxygen, chlorine or other elements including carbon and hydrogen: aldehydes, ethers, alcohols, esters, chlorofluorocarbons (CFCs) and 

hydrochlorofluorocarbons (HCFCs).

NORM

 Naturally Occurring Radioactive Materials, or NORMs, are those types of radioactive material to be found normally in nature, and which can expose people to radiation.  

Exposure to NORMs is often exacerbated by human activities, such as coal-mining, oil and gas production and the manufacture and use of fertilizers.   

There are examples of long-living radioactive elements, including uranium, potassium and thorium, and their associated decay products, such as radium and radon. These elements have always been present in the Earth’s crust, and in the tissues of all living creatures.    

Many natural materials contain radioactive elements (radionuclides). Although the individual level of exposure is usually harmless, problems can sometimes arrive when NORMs become concentrated as a result of human activity.  

Radioactive substances present in raw materials extracted from the ground can accumulate inside the equipment used in such processes, putting the workers involved at risk of exposure. If the individual is exposed to high concentrations of these substances over a prolonged period of time, the likelihood of him developing tumours or poisoning is considerable increased.