Unfortunately, the propane tank was leaking heavier-than-air propane gas into the water heater’s enclosure, and instead of lighting the pilot, Reynolds blew his house off its foundation and suffered burns over more than 50 percent of his body.
Heavier-than-air vapors can pose serious hazards at home or in the workplace because, unlike lighter-than-air gases (a category that includes the “lifting gases” like helium, hydrogen, ammonia, and hot air), heavier-than-air vapors don’t readily dissipate into the atmosphere.
If they find an area where the air is still, these vapors will simply aggregate at the bottom of an enclosure or along the floor of a room.
Even if they are not flammable, the vapors can pose a hazard to personnel in an enclosed space—they could displace enough oxygen to create a toxicity or asphyxiation hazard.
How can you identify and control heavier-than-air vapors in your workplace?
The weight of a vapor is called its “vapor density.” Dry air is defined as having a vapor density of one; typically, air contains a lot of water vapor, giving it a vapor density closer to 1.2 under most real-world conditions.
Gases with a vapor density greater than one are defined as heavier than air (although, as noted above, they may not actually be heavier than air in normal atmospheric conditions).
You can find a chemical’s vapor density in Section 9 of its safety data sheet (SDS), which lists its chemical and physical properties.
It can also be found in common chemical reference sources, such as the Merck Manual and the NIOSH Pocket Guide to Chemical Hazards.
Gases and vapors that are heavier than air will flow downhill and gather in pits, against dikes or walls, in swales, and in other low-lying, partially enclosed areas.
Pay attention to the vapor density of any chemicals in your facility that:
When these chemicals flow into low-lying areas, they can collect in sufficient concentrations to form a combustible, flammable, or explosive mixture.
They can also travel along the ground to a source of ignition and “flash back” to where they originated.
Enviro.BLR.com puts everything you need at your fingertips, including practical RCRA, CAA, CWA, hazardous waste regulatory analysis and activity, news, and compliance tools.
Hydrogen sulfide gas, carbon monoxide gas, and other toxic gases can accumulate in an enclosed space from the bottom upward.
Air quality testing at the workers’ breathing level can miss toxic levels of these gases while they are low to the ground, but if they continue to accumulate, toxic levels could develop in the breathing zone of workers.
Any chemical can be dangerous if it displaces oxygen within a space.
However, don’t overlook spaces that do not meet the definition of confined spaces but nonetheless might develop a dangerous atmosphere, such as basements and small or poorly ventilated rooms.
Most heavier-than-air vapors in these areas will not accumulate in high concentrations in the breathing zone of a person standing up, but employees who will be working near the floor may need to take precautions.
Tomorrow, we’ll look at strategies for controlling the hazards of heavier-than-air vapors.
Natural gas is one of the most flammable gasses in the world (source), comprised of 90% (or more) of methane.
It is odorless and widely used across the planet, making up almost a fifth of the world’s natural energy sources.
Surprisingly, many people do not know a lot about natural gas, despite its everyday usage.
Is natural gas heavier than air?
No, natural gas is not heavier than air, Its molecular weight ranges between 16-18.
It is a hydrocarbon mixture composed primarily of methane but includes other components like ethane and propane and small amounts of nitrogen and carbon dioxide.
The molecular weight of dry air is estimated to be just under 29.
You sniff the air, and you smell it: gas.
Someone probably left the stove on, and your apartment now smells of gas.
It also begs the question: What is there to know about natural gas?
Air is the general term used for the atmosphere around us.
Air is composed primarily of nitrogen and oxygen (at 99%), along with argon, carbon dioxide, neon, helium, krypton, hydrogen, and xenon that make up the remaining 1% (source).
To find out more about these gases, you can read, “What is the difference between Inert and Active Gas?”.
Due to the pressure of the air inside the balloon, the density of the air has increased (source).
What is Natural Gas Composed of?
Natural gas is highly combustible.
The average composition of natural gas includes 90% methane.
There may be trace elements of oxygen, nitrogen, and hydrogen sulfide (source).
Within the United States, Texas and Pennsylvania are the top two natural gas-producing states in the country.
Because of the high extraction of natural gas within the U.S, almost all gas used within the country originates within American borders (source).
A lot of natural gasses and oils originate from shale mining.
Shale is a sedimentary rock that contains organic material that generates oil and natural gas.
These accumulate over time, and processing can occur to obtain gas and oil.
Another type of natural gas is known as tight natural gas and originates from within the ground.
However, this gas comes from sandstone and carbonate reservoirs.
The bulk of natural gas produced in the U.S comes from shale.
Natural Gas Produced From The Earth
Natural gas is generally found deep within the earth.
Gas reservoirs are always located adjacent to oil wells, and the deeper the well, the higher the percentage of it will be gas (source).
Natural gas is non-renewable energy that has been growing in the earth’s crust for millions of years, and only in the last few centuries have humans been able to use it safely.
As organic remains decomposed and buried under layers of rock and dirt, the pressure on them created a process that changed the remains into hydrocarbon.
A protective layer of rock usually surrounds the reservoirs of natural gas, especially a “cap rock” on the top that keeps the gas pressurized and safe (source).
Other natural gas sources
Other natural gas sources
Gases found in the intestines of animals and humans, and low-oxygen areas of the planet, are examples of other natural gas sources.
Due to its lighter density, gas can be pulled from the ground or can slowly leak into the environment naturally.
One of the first recorded examples of natural gas usage was found by French explorers who discovered native Americans igniting gases that were seeping out of the area around Lake Erie in 1626 (source).
The Formation of Natural Gas
As mentioned before, they can originate from the pressure to organic matter that has been buried underground for thousands of years.
This process takes place through pressure placed on the organic matter by gathering layers of sediment and mud, along with increased temperatures closer to the earth’s core (source).
Another method for the formation of natural gas is through tiny microorganisms.
Biogenic methane is produced through this method.
Methanogens, which are tiny methane-producing microorganisms, break down organic matter.
Methanogens occur near the surface of the earth’s atmosphere, where there is no oxygen.
And unfortunately, a lot of the methane produced through this process escapes directly into the atmosphere.
However, new technologies are being developed to harvest the gases and decrease the environmental impact of methane release.
Abiogenic processes are another method of natural gas production.
This process involves the movement of hydrogen-based gases and carbon molecules.
The Natural Gas we Use
Natural Gas Flame
Natural gas works in many homes across the U.S, and almost 50% of the homes in America use natural gas for heating.
Since there is an abundant supply of gas across the world, the perception of natural gas is a more positive, cost-effective, and environmentally friendly method of energy production compared to other fossil fuels like coal and oil (source).
Gas is also a significant part of industries as it is used in the production of plastics, medicines, and antifreeze (source).
Gas is also used to produce electricity and is seen as a cleaner method compared to coal-powered plants.
New technologies have also allowed gas to produce heat and electricity at the same time, using gas at optimum levels and lessening the environmental impact.
Compressed Natural Gas (CNG) is another method of powering vehicles, especially heavy trucks, and transportation vehicles.
CNG releases far fewer carbon emissions compared to gasoline, and the primary disadvantage is that it does not produce the same level of energy compared to gas.
Across the world, the usage of gas is increasing, and predictions state that due to growth in China and Brazil, worldwide gas consumption will increase by 50% in the next 25 years (source).
However, the United States is still the number one consumer of natural gas, followed closely by Russia and China (source).
Therefore, safely producing gas and lessening its environmental impact is vital for the sustainable growth of the gas industry.
How Much Does Natural Gas Weigh Compared to Air?
Natural gas has a lower density than air.
It is primarily composed of methane, which is lighter than air (source).
A natural gas density calculator shows that natural gas weighs 0.712 kg/m³ (0.04457 lb/ft³) vs.
Natural gas can be cooled to about -260 degrees Fahrenheit and turned into liquified natural gas (LNG).
Natural Gas vs.
Some people may try to speak about natural gas and methane as synonyms, but they are different gases.
On the other hand, natural gas is primarily composed of methane, so the differences are minuscule.
Methane (CH₄) makes up most of the composition of natural gas.
Methane is released when organic matter decomposes (source).
However, these are actually due to the lack of oxygen rather than toxicity in the methane itself.
Methane occurs in two forms: organic and thermogenic.
Organic methane originates from sources such as landfills and marshes.
Human and animal waste products that ferment also release organic methane.
Thermogenic methane is formed in the deeper subsurface and produces natural gas through heat and pressure.
Smaller deposits of methane are found closer to the surface alongside oil, while deeper pure methane reservoirs occur at greater depths (source).
It is also known as a greenhouse gas, as it warms the earth’s atmosphere.
If it is released directly into the atmosphere, and not burnt, it is far more harmful to the environment compared to carbon dioxide (source).
While methane makes up a significant portion of natural gas, as mentioned before, natural gas also includes other components in its make up.
Natural gas also undergoes a process to remove harmful alkanes before it goes to work in households and businesses.
The methane in natural gas also gives it its buoyant quality.
Sources of Methane
Methane enters the atmosphere from a variety of sources.
Methane may not be the significant greenhouse gas emission in the creation of electricity, but a significant amount of methane releases into the atmosphere from this process.
These leaks, especially when not found and stopped quickly, can be extremely harmful to the environment.
Generally, the processed natural gas delivered to homes is almost entirely methane without other toxic chemicals.
Permafrost, soil frozen for more than two years, has started to defrost in the Arctic due to increasing temperatures.
When permafrost defrosts, organic material releases carbon dioxide and methane into the earth’s atmosphere (source).
Methane occurs and releases via livestock.
As the earth’s population grows, the desire for meat products is continually increasing.
These animals release methane into the atmosphere through their fecal matter.
In the United States alone, domestic livestock such as cattle, swine, sheep, and goats are the largest producers of methane emissions (source).
Our desire for meat is not the only contributor to methane emissions into the environment.
Human bodily functions also release methane into the atmosphere.
Organic waste sent to landfills, along with wastewater treatment plants, is both responsible for the CH₄ emissions (source).
Humans also cause the bulk of emissions through our actions, while other methane emissions come from natural sources.
There has been a massive spike in methane emissions since the year 1800, and we have caused more than a doubling of atmospheric methane levels since then (source).
Properties of Natural Gas
Natural gas is colorless, odorless, tasteless, and shapeless.
Natural gas is measured with British thermal units or Btu. One Btu is the amount of heat needed to increase the temperature of one pound of water by one degree Fahrenheit.
A cubic foot of gas is equal to about 1032 Btu (source).
Usually measured by volume, cubic feet is the unit of measure commonly used for natural gas.
Natural gas is equivalent to 8.003 pounds per cubic feet.
The autoignition temperature of natural gas is 1003 degrees Fahrenheit (source).
As mentioned before, natural gas is odorless.
It can prove to be dangerous since gas can be fatal.
In 1937, a gas leak caused an explosion at a school in New London, Texas.
It proved to be the catalyst for changing the functioning of the gas industry (source).
The natural gas has sulfur added, causing it to smell a little like rotten eggs.
The chemical mercaptan is used to odorize gas.
If you smell gas in an area, remove yourself and others from the space as quickly as possible, without turning on any appliances or lights, or anything that may create a spark.
A call to 911 should immediately occur, once you are out of range of the gas (source).
Through this article and many articles about natural gas, it has often been called the clean fossil fuel due to minimal emissions of carbon dioxide (CO2).
However, this title is unfair because of the damage that methane can do to the environment.
Methane is also a greenhouse gas and, even though it has a shorter lifetime in the atmosphere compared to carbon dioxide, it can cause more damage to the environment over 20 years compared to CO2 (source).
The gas can rise and trap heat in the upper atmosphere.
Methane is 86 times more potent than carbon dioxide in its effect on the environment for over 20 years.
While it is easy to say that gas is primarily burned, leaks, unfortunately, are part of the process of processing and distributing gas across countries and continents (source).
Studies have shown that the estimated amount of methane emissions has been miscalculated and is 60% higher than initially thought.
These emissions are almost equal to the damage that carbon dioxide has on the environment in the short term (source).
Leaks can take place at any point through the process of natural gas extraction, from leaks within the ground to leaks in pipes and storage containers.
Holes, such as the one in a Houston company in Louisiana, has steel tankers leaking massive amounts of LNG into the air, sparking fears that uncontrolled fires could be started (source).
In the United States, there are approximately 500,000 natural gas wells, along with 3 million kilometers of pipes.
These leave an almost infinite amount of possibilities of leaking natural gas into the environment (source).
The future of gas in the United States has been changing.
Gas has always been a significant part of the energy framework in the country and will continue to be part of it for the foreseeable future.
Some effort has occurred to minimize the environmental impact, but natural gas is far from the “clean” fossil fuel as the media depicts it.
As for the question about gas being lighter than air: If you ever wake up in a room full of gas, get on the floor, cover your mouth with a wet cloth and crawl your way out of the area.
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