Today, industrial gases are widely used in life and industrial production activities. Among them, the proportion of toxic gases is quite high. So, which gases are toxic, what are the criteria for classifying them as toxic gases? What is the list of some common toxic gases, and what are their effects on human health?

Let’s explore this interesting topic today with MIGCO.

What is toxic gas and how are toxic gases classified?

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Toxic gases are hazardous materials that can cause serious injury or even death. They are divided into 3 different groups depending on the level of impact on human health.

– Toxic gas type I:

These are toxic gases with a median lethal concentration (LC50) in air of 200 parts per million or less by volume of gas or vapor.

Or 2 milligrams per liter or less for fumes, mists, or dust. When inhaled continuously by white mice weighing approximately 200 to 300 grams for one hour (or less if death occurs within one hour).

– Toxic gas type II

Gases with a median lethal concentration (LC50) in air of at least 200 parts per million. But no more than 3,000 parts per million by volume of gas or vapor.

Or above 2 milligrams per liter of volume but no more than 30 milligrams per liter for dust, fumes, mists, when inhaled continuously by white mice weighing approximately 200 – 300 grams for 1 hour. (Or less if death occurs within one hour).

– Toxic gas type III

With a median lethal concentration (LC50) in air of more than 3,000 parts per million and not exceeding 5,000 parts per million per liter of gas or vapor.

Or above 30 milligrams per liter and not exceeding 50 milligrams per liter of dust or fumes when inhaled continuously by white mice weighing 200 – 300 grams for 1 hour (or less if death occurs within 1 hour).

List of toxic gases:

1. Toxic gas NO2 and NOx gases

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Nitrogen dioxide is a type I toxic gas with the chemical formula NO2, a reddish-brown liquefied gas with a pungent odor. It is extremely toxic, corrosive, and highly oxidizing, easily destroying enzymes, causing anemia, and cancer.

NO2 concentrations of about 50-100 ppm for less than 1 hour can easily cause pneumonia within 6-8 weeks.
150-200 ppm for less than 1 hour will destroy the trachea and lead to death if exposed for a prolonged period of 3-5 weeks.
Exposure to concentrations above 500 ppm for 2-10 days is likely to cause death.

In addition, other nitrogen oxides (NOx) such as NO (Nitric oxide) also pose a dangerous threat to human health. While N2 (Nitrogen) and N2O (Nitrous oxide) are not toxic, they can cause asphyxiation.

>> See more:What is NOx exhaust gas, NOx exhaust gas treatment methods

2. Toxic gas NH3

Ammonia is a type III toxic liquefied gas with a strong pungent odor, non-flammable and highly corrosive.

Exposure to high concentrations of NH3 in the air can cause burns to the mucous membranes of the nose, affecting the throat and respiratory tract, leading to respiratory failure.
Direct contact can cause severe burns leading to permanent blindness, lung disease, or death.
Swallowing it will cause burns in the mouth, stomach, and throat.

>> See more: What is NH3? What kind of substance is ammonia gas? Applications of NH3

3. Toxic gas H2S

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H2S is a colorless gas with a foul odor like rotten eggs, belonging to toxic gas group II.

How toxic is H2S gas?

Hydrogen sulfide is a very toxic gas (its toxicity is comparable to HCN and 5-6 times higher than CO), even a small amount in the air can cause rapid breathing, poisoning, and respiratory arrest in humans and animals.
High concentrations of H2S can paralyze the respiratory system, and the victim is prone to suffocation.

>> See more: What is H2S – hydrogen sulfide, where does it come from?

4. Toxic gas sarin

Sarin is a colorless and odorless toxic liquid with the chemical formula C4H10FO2P. Exposure to it will cause symptoms such as headache, nausea, respiratory arrest, suffocation, or permanent neurological damage.

5. How toxic is Chlorine gas

Cl2 is a compressed gas with a greenish color and an odor similar to bleach. It belongs to toxic substance group II, is corrosive and highly oxidizing.

Chlorine gas will cause itching, suffocation, and burning pain in the sternum, causing coughing, itching of the eyes and mouth, and excessive salivation.
Severe chlorine poisoning can cause headaches, epigastric pain, vomiting, jaundice, and even pulmonary edema.

6. VOCs (Volatile Organic Compounds) toxic gases

VOCs are volatile organic carbon-containing liquids, gases, or solids such as acetone, ethyl acetate, butyl acetate…

These toxic gases are less likely to cause chronic toxicity but cause acute toxicity with symptoms such as dizziness, nausea, eye swelling, muscle spasms, suffocation, or pneumonia.
Only a few toxic gases cause chronic toxicity, leading to leukemia or neurological diseases.

7. Asphyxiating gas CO2 – Carbon dioxide

This gas is familiar to all of us, present in life and all living and production activities. CO2 is a class IV gas, non-toxic, colorless, odorless, and tasteless, but easily causes asphyxiation.

>> See more: What is carbon dioxide – CO2? Applications of CO2 gas

8. Toxic gas SO2 (sulfur dioxide):

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SO2 can enter the respiratory tract or dissolve in saliva, through the digestive tract, and enter the bloodstream.

SO2 forms small particles of H2SO4 acid that enter the lymphatic system.
It causes disorders of sugar and protein metabolism, vitamin B and C deficiency, blood vessel obstruction, laryngeal stenosis, and difficulty breathing.

>> See more: What is SO2 (sulfurous gas)? What does it smell like? Applications and harmful effects of sulfur?

Some other harmful gases you should know:

Acetylene (C2H2) has a strong pungent odor, is a class IV toxic gas, unstable, and highly reactive.
Argon (Ar): Colorless, odorless, easily causes asphyxiation, belongs to class IV.
Arsine (AsH3): Colorless, sweet-smelling, belongs to toxic gas class I, is a very toxic gas, flammable and explosive.
Boron tribromide (BBr3): Colorless gas class II, toxic and corrosive.
Boron trichloride (BCl3): Colorless, corrosive, and belongs to toxic gas class III.
Boron trifluoride (BF3): Pungent odor, strong irritant, is a class II toxic gas with high corrosiveness.
Bromine (Br2): Dark brown liquid, pungent odor, highly oxidizing, toxic, corrosive
Carbon monoxide (CO) belongs to class 3, is a colorless, odorless, and tasteless toxic gas, flammable.
Chlorine dioxide (ClO2): Odor similar to chlorine, is a class II toxin and an oxidizing agent.
Chlorine trifluoride (ClF3): Pungent odor, class II toxin with high oxidizing and corrosive properties.
Deuterium (H2) belongs to class IV, colorless and flammable
Diborane (B2H6): Class I hazardous liquefied gas, odorless but very toxic, flammable and explosive
Dichlorosilane belongs to class II with the chemical formula SiH2Cl2 (HCl), toxic, corrosive, and flammable
Ethane (C2H6) is a class IV non-toxic gas, colorless, odorless, and highly flammable.
Ethylene (C2H4)
Ethylene oxide: C2H40
Fluorine: F2
Germane: GeH4
Helium: He causes asphyxiation
Hydrogen, Hydrogen bromide, Hydrogen chloride, Hydrogen cyanide, Hydrogen fluoride, Hydrogen iodide, Hydrogen selenide, Hydrogen sulfide, Krypton, Methane, Methyl bromide, Methyl chloride, Methyl isocyanate, Methyl mercaptan, Neon, Nickel carbonyl,…