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GAS identification (over 400 detectable gases)

Carboys of various gases

The detection of dangerous gases or toxic for health is possible. This detection can be done using colorimetric test tubes, dosimetric tubes. Colorimetric test tubes are devices for the spot measurement of gases. These tubes are specific for a particular gas. They measure in seconds the precise concentration of a gas present in the air. This measurement system requires a hand pump to perform the sampling. This type of device is generally used to determine the presence of toxic or asphyxiating gases. Dosimetric tubes measure the mean exposure values (MEV). They therefore make it possible to evaluate the presence of a gas over a period determined according to the needs. Each tube is specific for a type of gas.

Methane (CH4)

Methane is a colorless, odorless and flammable gas. Generally, it adds an odorant to allow its detection during gas leakage. It is a greenhouse gas (GHG). In 2005, in Quebec, it accounted for 12.1% of GHGs released into the air. Fossil deposits are the main sources of methane. It therefore comes from the decomposition of organic matter that has occurred for millions of years. He composes what is called "natural gas". Its composition varies according to the nature of the fossilized organic matter and the physicochemical conditions of the environment. For example, in Quebec, the natural gas used consists of 95.4% methane, 1.8% ethane, 1.9% nitrogen, 0.7% carbon dioxide and 0.2% a simple hydrocarbon mixture such as butane, propane and isobutane.

Natural gas is found everywhere in the domestic, industrial and agricultural sectors. It is mainly marketed in the form of compressed gas.

Methane is used in the chemical industry for the synthesis or manufacture of many products including:

  • Acetylene
  • Methanol
  • Ethanol
  • Ammonia
  • Chloroform
  • Hydrogen cyanide
  • Methyl chloride
  • Methylene chloride
  • Carbon black

Methane is also used in various processes, such as:

  • Production of chemical vapor deposition of carbide and diamond films.
  • The manufacture of synthetic proteins.

In the workplace, exposure to methane is mainly in the gaseous state. Methane is an asphyxiating gas since it replaces oxygen in the air when it is absorbed by the body.

Chlorine (Cl)

Chlorine gas is used as a disinfecting and sterilizing agent in water treatment. It also serves as a raw material for the synthesis of many organic and inorganic compounds. In Quebec, it has long been used as a bleaching agent for pulp and paper.

The most common exposure to this gas occurs as a result of accidental mixing or when opening containers of solid calcium hypochlorite or trichloroisocyanuric acid (granular pool chlorine). Chlorine is very toxic and can be fatal if inhaled. It is corrosive to the respiratory tract. When an individual experiences severe short-term exposure to long-term effects on the respiratory tract can be observed. Chlorine is also corrosive to skin and eyes causing burns.

Chlorine dioxide (ClO2)

Chlorine dioxide is mainly used as a bleaching agent in the pulp and paper industry. It can also be used (restricted use):

  • In laundering of textile fibers
  • As a disinfectant in several drinking water plants
  • In the food industry for microbial control
  • In the oilfields to remove biofilms, control odors or neutralize certain compounds

In the workplace, exposure to chlorine dioxide is mainly through inhalation or skin contact with gas. Chlorine dioxide is irritating and corrosive to the skin, eyes, respiratory and digestive tract. Generally, the severity of symptoms varies with exposure (duration of contact, concentration of the product, etc.). Chlorine dioxide can cause severe burns, ulcers, necrosis or scars that may be permanent on the skin. Generally, burns or eye injuries are irreversible until they cause blindness (blindness). When this gas enters the lungs, it can cause pulmonary edema (mainly coughing and breathing difficulties) that often occur after up to 48 hours.

Formaldehyde (CH2O)

Formaldehyde is a colorless gas commonly used around the world as a disinfectant and preservative. It is also used in many cleaning products and some building materials. When present at high levels in the air, it gives off a pungent odor. Formaldehyde is found at low rates in all buildings. Formaldehyde is an irritant. Short-term exposure to high levels of formaldehyde can cause burning sensations in the eyes, nose and throat. Long-term exposure to moderate levels of formaldehyde may be associated with breathing problems and allergies, especially in children.

Carbon monoxide (CO)

This toxic gas is invisible and odorless and does not irritate. It is therefore impossible to detect its presence in the air without a detection device. It is therefore strongly recommended to install CO alarms in houses with combustion appliances. Carbon monoxide (CO), from the operation of a car in a garage or a faulty heater, is a dangerous poison gas because of its asphyxiating properties. It accumulates rapidly in the blood and prevents oxygen from being carried by the red blood cells and thus to oxygenate the individual.

  • Slight exposure: headache, runny nose, eye irritation, flu-like symptoms, etc.
  • Average exposure: drowsiness, dizziness, vomiting, disorientation, confusion, etc.
  • Strong exposure: fainting, brain injury, death.

Nitrogen dioxide (NO2)

This gas may be present in the indoor environment by the use of combustion apparatus. This gas can also be produced by a vehicle that is allowed to operate in a garage. Nitrogen dioxide can aggravate asthma symptoms, reduce the proper functioning of the respiratory system (coughing, wheezing) ... The best prevention is to properly maintain the appliances on an annual basis and to avoid using any equipment. Combustion in enclosed spaces, not ventilated or even poorly ventilated. Nitrogen dioxide exposure in the workplace is caused mainly by its vapors. Some sectors of the industry can contribute to the emission of nitrogen dioxide into the air. Workers involved in these industries are subject to significant exposure to this gas.

  • The use of nitro explosives in mines and on hydroelectric sites
  • Incineration of garbage in incinerators and cement plants
  • Use of coal, gas or other hydrocarbon heaters
  • The fermentation of grain stored in silo.

Carbon dioxide (CO2)

Carbon dioxide, a colorless and odorless gas, is a normal constituent of the atmosphere found at concentrations ranging from 350 to 400 ppm. In the indoor environment, carbon dioxide is mainly produced by the occupants themselves. The concentration of CO2 in the air can, under certain conditions, be a good indicator of the efficiency of the ventilation system; it is expressed in parts per million (ppm). To achieve acceptable indoor air quality, it is recommended that CO2 levels not exceed 700 ppm higher than outdoor rates. CO2 is only toxic at high concentrations (ASHRAE Standard 62-1989 (Ventilation for Acceptable Indoor Air Quality) recommends a minimum ventilation rate of 10 liters / second per person for IAQ in offices; can be obtained by the ventilation method ASHRAE also proposes another method: the IAQ procedure is to use acceptable concentrations of certain contaminants to obtain a good IAQ. In normal operation, the minimum outdoor ventilation rate of 10 liters / second per person would give a carbon dioxide concentration of 850 ppm in a steady state of occupied space.

A pronounced state of discomfort results in a clear difficulty in breathing and appears when one reaches a concentration of 10,000 ppm of CO2; note that this state of discomfort varies a lot from person to person

Green smoke representing toxic gas

Hydrogen sulphide (H2S)

Hydrogen sulphide is a dangerous gas. It is naturally formed during the decomposition of organic matter and during industrial processes. In low concentration, it smells like rotten eggs. On the other hand, the smell of workers is not an indication of the concentration of this gas in the air. This gas when inhaled can go into the bloodstream. Poisoning can occur when concentrations are too high, preventing the body from properly eliminating it naturally.

Exposure to low levels of hydrogen sulfide leads to headache, dizziness, loss of balance, agitation, nausea and diarrhea. Chronic exposure to low concentrations can lead to chronic intoxication whose symptoms are a slowdown in heart rate, fatigue, insomnia, cold sweats, eye infections, weight loss ... When intoxication is detected in time, the individual can be treated and the effects will be reversible. When there is acute intoxication, some individuals may have long-term symptoms such as memory loss, depression, and paralysis of some facial muscles.

Workers who are generally exposed to this gas are those who work in sewers, in wastewater treatment plants ... In addition, excavation workers who work in open areas with high levels of organic matter (wetlands, landfills) may be exposed.

Other examples of gas

Hydrochloric acid (HCl)
Hydrogen fluoride (HF)
Ammonia (NH3))
We can identify the presence of 400 different gases in an industrial environment.