Methane (CH₄): Properties, Applications, and Hazards. A Complete Overview

Introduction

Methane (CH₄) is a gas we encounter every single day, often without even noticing. It burns in the burners of our kitchen stoves, heats our homes, and serves as a raw material for producing fertilizers and plastics. At the same time, it seeps out of swamps, accumulates in coal mines, and, unfortunately, sometimes causes devastating explosions in residential buildings.

Methane is the simplest representative of the alkane class (saturated hydrocarbons) and the primary component of natural gas. Its share in natural gas can reach up to 98% by volume. Despite its apparent simplicity — just one carbon atom and four hydrogen atoms — this gas plays a colossal role in the global energy sector, the chemical industry, and, regrettably, in climate change.

In this article, I have compiled the most comprehensive information on methane: from its physicochemical properties to safety issues and climate impact.

Physical Properties of Methane

Under normal conditions, methane is a colorless gas with no taste or smell. It is almost twice as light as air: the relative density of methane compared to air is 0.554 at 20 °C. This is why, during leaks, methane does not creep along the floor but rises and accumulates under the ceiling or the upper stories of buildings.

Methane dissolves poorly in water — only 3.3 mL per liter at 20 °C — but it is readily soluble in ethanol, ether, and other organic solvents.

The main physical parameters of methane are summarized in the table:

Parameter	Value
Chemical Formula	CH₄
Molar Mass	16.04 g/mol
State at Normal Conditions	Colorless gas
Gas Density (0 °C, 1013 hPa)	0.72 kg/m³
Relative Density (air = 1, 20 °C)	0.554
Melting Point	–182.5 °C
Boiling Point	–161.5 °C
Solubility in Water (20 °C)	3.3 mL/L
Heat of Combustion	~56 MJ/kg

Liquefied Natural Gas (LNG) is methane cooled to cryogenic temperatures (–161.5 °C). In a liquid state, methane occupies roughly 600 times less volume than in a gaseous state, making its transportation by tankers over vast distances possible. Upon contact with skin, liquid methane causes instantaneous frostbite.

Chemical Properties of Methane

Methane is a chemically rather inert substance under ordinary conditions, which is explained by the strength of the C–H bonds in its molecule.

The methane molecule has the shape of a regular tetrahedron with a carbon atom in the center and hydrogen atoms at the vertices. It is one of the most symmetrical and stable organic molecules.

Methane is not toxic as such, but at high concentrations, it causes asphyxiation by displacing oxygen from the air.

Combustion — The Main Chemical Reaction

The primary and most important reaction of methane is combustion:

CH₄ + 2O₂ → CO₂ + 2H₂O + 56 MJ/kg

Complete combustion of methane produces only carbon dioxide and water, and the flame has a faint bluish hue. It is this reaction that provides us with heat and electricity. Incomplete combustion (lack of oxygen) produces carbon monoxide (CO), which poses a mortal danger to humans.

Other Important Reactions

At high temperatures, methane is capable of entering into reactions that form the basis of large-scale industrial processes:

• Steam Reforming — the reaction of methane with steam at high temperature and pressure in the presence of a nickel catalyst. This produces synthesis gas — a mixture of CO and H₂. This is a key process for the entire nitrogen industry: ammonia (NH₃), methanol (CH₃OH), and hydrogen are then produced from the synthesis gas.

• Halogenation Reactions — in the presence of light, methane enters into substitution reactions with chlorine and bromine. By sequentially replacing hydrogen atoms, methyl chloride, chloroform, and carbon tetrachloride can be obtained — important industrial solvents and intermediates for organic synthesis.

The auto-ignition temperature of methane is 537.8 °C. This means that upon contact with a surface heated to this temperature, a methane-air mixture will ignite without any spark.

How Methane Is Given an Odor: Odorization

Methane itself has no smell. If not for special additives, a household gas leak would be impossible to detect in time — until the concentration reaches an explosive threshold or until a person begins to suffocate from lack of oxygen.

To give us a chance to notice the danger in time, odorization was invented — the addition of special odorous substances — odorants — to methane (natural gas).

In Russia and the post-Soviet countries, ethyl mercaptan (C₂H₅SH) is traditionally used for this purpose — a colorless, transparent liquid with such a sharp and unpleasant odor that the human nose can detect it even at a negligible concentration. Descriptions often compare it to the smell of rotten cabbage or garlic.

The gas odorization standard in Russia is 16 grams of ethyl mercaptan per 1000 cubic meters of gas. The system is designed so that the pungent odor should be clearly noticeable at a gas concentration in the air not exceeding 1/5 of the lower flammability limit. Simply put, you will smell the gas long before the methane concentration becomes dangerous.

In addition to ethyl mercaptan, tetrahydrothiophene (THT), dimethyl sulfide (DMS), and other sulfur-containing compounds are also used as odorants. The choice of a specific odorant depends on the gas composition, climatic conditions, and local regulations.

Applications of Methane

Methane is not just fuel for a stove. It is the backbone of several industries and one of the main energy carriers of modern civilization.

Energy

The main volume of extracted methane is burned to produce heat and electricity. Gas turbines at thermal power plants, boiler houses, household stoves, and heating boilers — all run on methane. Among fossil fuels, natural gas is considered the most environmentally friendly, as its combustion produces virtually no soot, sulfur compounds, or other solid particles.

Chemical Industry

Methane is a critical raw material for the chemical industry. Through the steam conversion stage, it is transformed into synthesis gas, from which the following are then produced:

• Ammonia (NH₃) — the basis for the production of nitrogen fertilizers, without which modern agriculture would be impossible.

• Methanol (CH₃OH) — one of the basic products of organic synthesis, a raw material for plastics, solvents, and formaldehyde.

• Hydrogen (H₂) — a promising energy carrier, which I wrote about in detail in one of the previous articles.

• Acetylene (C₂H₂) — a gas for welding and cutting metals, and a raw material for plastics production.

• Carbon black (soot) — used in the production of automobile tires, paints, and pigments.

Furthermore, methane is used to produce chlorine derivatives, which serve as industrial solvents and as raw materials for obtaining fluoroplastics — unique chemically resistant polymers.

Transport

Compressed (CNG) and liquefied (LNG) natural gas are increasingly being used as motor fuel for cars, buses, and even marine vessels. Compared to gasoline and diesel, methane is significantly cheaper and more environmentally friendly.

Residential and Utility Sector

The household gas supplied to apartments through gas distribution networks is the same methane, purified and odorized.

The Hazards of Methane

Explosiveness

Methane is a flammable gas. Moreover, it forms explosive mixtures with air. The flammability limits of methane in air are: lower — from 4 to 5% by volume, upper — from 15 to 16%. This means that if 5 to 15% of methane by volume accumulates in a room, a single spark is enough to trigger an explosion. The most explosive concentration is 9.5% by volume.

Anything can serve as a source of ignition: turning a light switch on or off, a phone ringing, a static electricity discharge from clothing, or a spark from metal striking metal. This is precisely why the use of open flames and electrical appliances is strictly prohibited in rooms where a gas leak is possible.

The ignition temperature of methane is 695–742 °C. However, even at lower temperatures, methane can ignite upon prolonged contact with a hot surface.

Impact on Human Health

Methane is not classified as a toxic gas. Its hazard class is 4 (low-toxicity substance). However, this does not make it safe. The main danger of methane to humans is asphyxiation.

Being lighter than air, methane, when accumulating in a confined space, displaces oxygen. When the methane concentration in the air exceeds 20%, it has a suffocating effect on a person. The first signs of oxygen starvation are dizziness, increased respiration, and impaired motor coordination. Without timely evacuation from the contaminated area and medical assistance, a fatal outcome is possible.

The risk of asphyxiation is particularly relevant in confined spaces — basements, wells, technical galleries, and mines — where a sudden release of methane can reduce the oxygen concentration to a critical level.

Upon contact with liquid methane (LNG), there is a risk of frostbite to the skin and eyes due to the extremely low temperature (–161.5 °C).

Methane as a Greenhouse Gas

In addition to its explosiveness, methane poses another global threat: it is the second most significant greenhouse gas after carbon dioxide (CO₂).

The contribution of methane to current global warming is estimated at 19%, while the contribution of CO₂ is 64%. However, in terms of the strength of its greenhouse effect, methane significantly surpasses carbon dioxide. One ton of methane is equivalent to approximately 28–34 tons of CO₂ in terms of global warming potential over 100 years. Over a shorter, 20-year period, the warming activity of methane exceeds that of CO₂ by a factor of 86.

The main sources of methane emissions into the atmosphere are: leaks during natural gas extraction and transportation, coal mines, municipal solid waste landfills (organic decomposition), agriculture (ruminant animals, rice paddies), and wetland and natural ecosystems.

Given the high warming potential of methane, controlling leaks at all stages — from extraction to consumption — is a critical environmental task.

Safety When Working with Methane

Given the explosiveness of methane, working with it requires strict compliance with safety rules. Key measures include:

• Continuous monitoring of the methane concentration in the workplace air. At gas extraction, transportation, and consumption facilities, gas analyzers are installed that measure the volumetric fraction of methane in the air and sound an alarm when the safe threshold is exceeded. In coal mines, for example, automatic gas monitoring systems are used that constantly track the methane concentration.

• Forced ventilation of premises where methane accumulation is possible.

• Explosion-proof electrical equipment and lighting, and the use of non-sparking hand tools.

• Timely evacuation of personnel from the hazardous area upon alarm activation.

• Use of personal protective equipment — at high concentrations, self-contained breathing apparatuses are used.

Conclusion

Methane is, without exaggeration, the foundational gas of our civilization. It warms our homes, provides electricity, and serves as a raw material for fertilizers and countless chemical products. But, like any powerful tool, it demands respect and strict adherence to safety regulations.

Its explosiveness is not a theoretical threat but a reality that annually claims human lives. Its warming potential is a long-term challenge affecting the climate of the entire planet. And its physical nature — a colorless and odorless gas impossible to detect without instruments or special odorants — makes an invisible leak particularly insidious.

Understanding the properties of methane, its behavior under various conditions, and the rules for safe work with it is essential for anyone connected in any way with gas equipment, industrial safety, or environmental monitoring.