What gases can be dangerous and why? What comes to mind is that the answer may be relative. Depending on the experience of a chemist with hazardous gases, the answer may be subjectively biased to that experience.
When you think about the question a bit, the most satisfactory answer would be that all gases are dangerous. The interesting part is answering why. Obviously there are gases that are toxic, others that are corrosive, and others that are flammable and cause explosions.
The Canadian company International Sensor Technology published on its website a list of more than 50 gases that pose a risk, yet this list is not complete (International Sensor Technology, SF).
At first, all gas, even the most harmless, represents a risk depending on its concentration and the ventilation of the place where it is, since it has the ability to displace oxygen and suffocate the victim.
Even oxygen itself is highly dangerous since, as an oxidizing agent, its presence fuels the flame in a fire and despite the fact that it is the essential compound for life, oxidative reactions also destroy cells, causing aging and ultimately death (airgas, 2017).
Gas handling
One of the factors that makes a gas dangerous is its mishandling. An inexperienced or careless person can put themselves or others at risk by improperly handling a gas.
Not only that, improper handling of gases can contribute to environmental pollution if established regulations are not followed.
The risk that can arise when handling or using a gas can be classified into three different categories:
1- Toxic gases
These are gases that are harmful to humans when inhaled or ingested in various amounts.
This includes gases like ammonia, chlorine, sulfur, and many others. The official definition of toxic gas is:
'A compressed gas or vapor that has a lethal average concentration (LC50) in air of 200 parts per million (ppm) by volume, or 2 milligrams per liter of mist, smoke or dust, when administered by continuous inhalation for one hour (or less if death occurs within an hour) to albino rats weighing between 200 and 300 grams each.
The toxicity of a gas will depend on its concentration. There may even be poisoning by technically harmless gases such as nitrogen or noble gases if the concentration is high and there is no proper ventilation.
In Jules Verne's book From the Earth to the Moon, two American scientists and a French adventurer embark on a trip to the moon in a cannonball fired in Florida.
In one part of the story, the French adventurer increases the concentration of oxygen causing attacks of hysteria and fainting spells that occur in reality (Verne, 2008).
One must be especially careful when handling toxic gases and avoid minimal exposure.
It is necessary to use the suitable equipment like artificial respirators and to work under hood. In the event of an accident, proper first aid techniques should be applied and immediate medical attention obtained.
2- Flammable gases
These gases are capable of burning in certain concentrations. Flammable gases only burn in the presence of oxygen.
Examples of flammable gases are methane, propane, butane, and acetylene. Many of these gases lack aroma, which increases their danger. Cases of poisoning or fires due to gas leaks have been reported.
Gases can also be combustible. This category of dangerous gases includes all gases that can explode in certain concentrations. Like flammable gases, combustible gas requires the presence of oxygen.
Be careful with ignition sources when handling this type of gas and you should never smoke in their presence. It is advisable to work under a hood.
The gases are stored and transported in pressurized cylinders. Misuse of these cylinders can cause explosions (Canadian Center for Occupational Health & Safety, 2017).
Even household gases such as insecticides and flavorings can pose a risk if stored near a heat source that expands the gas causing an explosion.
3- Oxidizing gases
This type of gas has the property of increasing the flame. The presence of these gases increases the risk of fire and also that they can react violently causing explosions.
They should be handled with extreme care and stored away from strong oxidizing substances, acids or bases (GASDETECTIONSYSTEMS, 2012).
Figure 1: signs of toxic risk (right), flammable risk (center) and oxidizing agent (left)
Uses of gases
The other factor that can make a gas dangerous is its improper use. Of course, the worst use of gas is to hurt or kill others.
Since the dawn of war, people have sought new ways to kill each other. As early as 600 BC, the Athenians were poisoning the wells of the Spartans, who later attempted to release toxic sulfur gases onto the walls of Athens, hoping to fill the city with toxic smoke.
Genghis Khan used the same trick, launching sulfur catapults during the siege of fortified cities around AD 1200 (Maass, 2013).
Although chemicals have been used as tools of warfare for thousands of years, modern chemical warfare has its genesis on the battlefields of World War I.
During World War I, chlorine and phosgene gases were released from boats on the battlefield and dispersed by the wind.
These chemicals were manufactured in large quantities at the beginning of the century and were deployed as weapons during the prolonged period of trench warfare (Organization for the prohibition of chemical weapons, SF).
The first large-scale chlorine gas attack occurred on April 22, 1915 at Ypres in Belgium. The Allies saw how the gases could be effective, and began to use them. Both sides switched to phosgene, a choking agent, and mustard gas, which causes painful burns and blisters.
By the end of the Great War - dubbed by historians as "the war of the chemicals" - more than 90,000 soldiers had been killed by the poison gas, many succumbing only after days or weeks of agony. A million more were injured, many blinded for life.
The horror of the world led the League of Nations in 1925 to draft the Geneva Protocol, banning chemical weapons in war and declaring that their use "has been justly condemned by the general opinion of the civilized world." Most nations signed (EVERTS, 2015).
Figure 2: American soldiers during World War I stage a photo illustrating the bad effects of forgetting the gas mask. Bettmann / CORBIS
During World War II, concentration camps used hydrogen cyanide gas, also known as Zyclon B, in gas chambers during the Holocaust.
Hydrocyanic acid was used in US gas chambers and its toxicity lies in the fact that cyanide binds covalently to the heme group in the blood, displacing oxygen, causing drowning (Baglole, 2016).
Recently, there was a chemical weapons attack in the town of Khan Sheikhoun, in the Idlib province in Syria, which, according to the US government, was carried out by Syrian aircraft unleashing a missile attack by the US government.
The chemical agent used is thought to be sarin gas, a nerve gas that is considered 20 times more lethal than Zyclone B (BBC Mundo, 2017).
References
- (2017, January 27). SAFETY DATA SHEET Oxygen. Recovered from airgas.com.
- Baglole, J. (2016, September 8). Deadly and Controversial Chemical Weapons Recovered from thebalance: thebalance.com.
- BBC World. (2017, April 7). 5 questions left by the reported chemical weapons attack in Syria. Recovered from bbc: bbc.com.
- Canadian Center for Occupational Health & Safety. (2017, May 9). Compressed Gases - Hazards. Recovered from ccohs.ca.
- EVERTS, S. (2015). A Brief History of Chemical War. Recovered from chemheritage.
- (2012, May 17). Hazardous Gas Definition. Recovered from gasdetectionsystems.
- International Sensor Technology. (SF). list of hazardous gases. Retrieved from intlsensor.
- Maass, H. (2013, September 13). A brief history of chemical warfare. Recovered from theweek.
- Organization for the prohibition of chemical weapons. (SF). Brief History of Chemical Weapons Use. Recovered from opcw.org.
- Verne, j. (2008). From the earth to one. Madrid: AKAL.