Many people know that death during a fire occurs more often due to poisoning from combustion products than from thermal exposure. But you can poison yourself not only during a fire, but also in everyday life. The question arises of what types of combustion products exist and under what conditions they are formed. Let's try to figure this out.
What is combustion and its product?
You can endlessly look at three things: how water flows, how other people work, and, of course, how fire burns ...
Combustion is a physicochemical process based on a redox reaction. It is accompanied, as a rule, by the release of energy in the form of fire, heat and light. In this process, a substance or a mixture of substances that burn is involved - reducing agents, as well as an oxidizing agent. Most often, this role belongs to oxygen. Burning can also be called the process of oxidation of burning substances (it is important to remember that combustion is a subspecies of oxidation reactions, and not vice versa).
Combustion products are all that is released during combustion. Chemists in such cases say: "Everything that is on the right side of the reaction equation." But this expression is not applicable in our case, since, in addition to the redox process, decomposition reactions also occur, and some substances simply remain unchanged. That is, combustion products are smoke, ash, soot, emitted gases, including exhaust. But the special product is, of course, energy, which, as noted in the last paragraph, is emitted in the form of heat, light, fire.
Substances emitted during combustion: carbon oxides
There are two carbon monoxide: CO 2 and CO. The first is called carbon dioxide (carbon dioxide, carbon monoxide (IV)), since it is a colorless gas consisting of carbon completely oxidized by oxygen. That is, carbon in this case has a maximum oxidation state - the fourth (+4). This oxide is a combustion product of absolutely all organic substances, if they are in excess oxygen during combustion. In addition, carbon dioxide is released by living things when breathing. By itself, it is not dangerous if its concentration in the air does not exceed 3 percent.
Carbon monoxide (II) (carbon monoxide) - CO is a toxic gas in the molecule of which carbon is in the oxidation state +2. That is why this compound can "burn out", that is, continue the reaction with oxygen: CO + O 2 = CO 2 . The main dangerous feature of this oxide is its incredibly large ability, in comparison with oxygen, to bind to red blood cells. Red blood cells are red blood cells whose task is to transport oxygen from the lungs to the tissues and vice versa, carbon dioxide to the lungs. Therefore, the main danger of oxide is that it interferes with the transfer of oxygen to various organs of the human body, thereby causing oxygen starvation. It is CO that most often causes poisoning by combustion products in a fire.
Both carbon monoxide are neither color nor odor.
Water
The well-known water - H 2 O - is also released during combustion. At a combustion temperature, products are released in the form of gas. And water is like steam. Water is a combustion product of methane gas - CH 4 . In general, water and carbon dioxide (carbon monoxide , again it all depends on the amount of oxygen) are mainly released during the complete combustion of all organic substances.
Sulfur gas, hydrogen sulfide
Sulfur gas is also an oxide, but this time sulfur is SO 2 . It has a large number of names: sulfur dioxide, sulfur dioxide, sulfur dioxide, sulfur dioxide. This combustion product is a colorless gas with a pungent smell of a lit match (it is released when it ignites). Anhydride is released during the combustion of sulfur, sulfur-containing organic and inorganic compounds, for example, hydrogen sulfide (H 2 S).
When it enters the mucous membrane of a person’s eye, nose or mouth, the dioxide easily reacts with water, forming sulfurous acid, which decomposes readily, but at the same time manages to irritate receptors and provoke inflammatory processes of the respiratory tract: H 2 O + SO 2 ⇆ H 2 SO 3 . This is due to the toxicity of the sulfur combustion product. Sulfur gas, like carbon monoxide, can burn - oxidize to SO 3 . But this happens at a very high temperature. This property is used in the production of sulfuric acid at the plant, as SO 3 reacts with water, forms H 2 SO 4 .
But hydrogen sulfide is released during the thermal decomposition of some compounds. This gas is also poisonous, has a characteristic smell of rotten eggs.
Hydrogen cyanide
Himmler then clenched his jaw, bit the ampoule with potassium cyanide, and died a few seconds later.
Potassium cyanide is the strongest poison - a salt of hydrocyanic acid, also known as hydrogen cyanide - HCN. It is a colorless liquid, but very volatile (easily turning into a gaseous state). That is, during combustion, it will also be released into the atmosphere in the form of gas. Hydrocyanic acid is very toxic, even a small one - 0.01 percent - the concentration in the air is fatal. A distinctive feature of acid is the characteristic smell of bitter almonds. Appetizing, isn't it?
But hydrocyanic acid has one peculiarity - it can be poisoned, not only by inhaling directly by the respiratory system, but also through the skin. So it’s impossible to defend yourself only with a gas mask.
Acrolein
Propenal, acrolein, acrylaldehyde - all these are the names of one substance, an unsaturated aldehyde of acrylic acid: CH2 = CH-CHO. This aldehyde is also a highly volatile liquid. Acrolein is colorless, with a pungent odor, and is very toxic. If liquid or its vapor enters the mucous membranes, especially in the eyes, it causes severe irritation. Propenal is a highly reactive compound, and this explains its high toxicity.
Formaldehyde
Like acrolein, formaldehyde belongs to the class of aldehydes and is an aldehyde of formic acid. This compound is also known as methanal. It is a toxic, colorless gas with a pungent odor.
Nitrogen-containing substances
Most often, during the combustion of substances containing nitrogen, pure nitrogen is released - N2. This gas is already contained in large quantities in the atmosphere. Nitrogen may be an example of an amine combustion product. But during thermal decomposition, for example, of ammonium salts, and in some cases even during combustion itself, its oxides are also emitted into the atmosphere, with the degree of nitrogen oxidation in them plus one, two, three, four, five. Oxides are gases, have a brown color and are extremely toxic.
Ashes, ash, soot, soot, coal
Soot, or soot, is the remnant of carbon that has not reacted, for various reasons. Soot is also called amphoteric carbon.
Ashes, or ashes, are small particles of inorganic salts that are not burnt or decomposed at a combustion temperature. When fuel burns out, these micro-compounds become suspended or accumulate at the bottom.
And coal is a product of incomplete combustion of a tree, that is, its remains that have not burned, but which are still capable of burning.
Of course, this is far from all the compounds that are released during the combustion of certain substances. It is unrealistic to list them all, and it is not necessary, because other substances are released in negligible amounts, and only during the oxidation of certain compounds.
Other mixtures: smoke
Stars, forest, guitar ... What could be more romantic? And one of the most important attributes is missing - a bonfire and a stream of smoke above it. What is smoke?
Smoke is a mixture that consists of gas and particles suspended in it. In the role of gas are water vapor, carbon monoxide and carbon dioxide and others. And solid particles are ashes and just not burned residues.
Traffic fumes
Most modern cars operate on an internal combustion engine, that is, the energy generated by the combustion of fuel is used for movement. Most often it is gasoline and other petroleum products. But when burned out, a large amount of waste is released into the atmosphere. This is the exhaust fumes. They are released into the atmosphere in the form of smoke from the exhaust pipes of a car.
Most of their volume is nitrogen, as well as water, carbon dioxide. But toxic compounds are also emitted: carbon monoxide, nitrogen oxides, unburned hydrocarbons, as well as soot and benzpyrene. The last two are carcinogens, that is, they increase the risk of cancer.
Features of products of complete oxidation (in this case, combustion) of substances and mixtures: paper, dry grass
When paper is burned, carbon dioxide and water are also mainly released, and when there is a lack of oxygen, carbon monoxide. In addition, the paper contains adhesives that can be released and concentrated, and resins.
The same situation occurs when hay is burned, only without adhesives and tar. In both cases, the smoke is white with a yellow tint, with a specific smell.
Wood - firewood, boards
Wood consists of organic substances (including sulfur and nitrogen) and a small amount of mineral salts. Therefore, with its complete combustion, carbon dioxide, water, nitrogen and sulfur dioxide are released; gray and sometimes black smoke with a tarry odor, ash is formed.
Sulfur and Nitrogen Substances
About toxicity, combustion products of these substances, we have already said. It is also worth noting that when burning sulfur, smoke is released with a grayish-gray color and a pungent smell of sulfur dioxide (since it is sulfur dioxide that is released); and when burning nitrogenous and other nitrogen-containing substances, it is yellow-brown, with an irritating smell (but smoke does not always appear).
Metals
During the combustion of metals, oxides, peroxides or superoxide of these metals are formed. In addition, if the metal contained any organic or inorganic impurities, then the products of combustion of these impurities are formed.
But magnesium has a burning feature, since it burns not only in oxygen, like other metals, but also in carbon dioxide, forming carbon and magnesium oxide: 2 Mg + CO 2 = C + 2MgO. Smoke forms white, odorless.
Phosphorus
When phosphorus is burned, white smoke smells like garlic. In this case, phosphorus oxide is formed.
Rubber
And, of course, rubber. The smoke from burning rubber is black due to the large amount of soot. In addition, the products of combustion of organic substances and sulfur oxide are released, and thanks to it, the smoke acquires a sulfuric odor. Heavy metals, furan and other toxic compounds are also released.
Classification of toxic substances
As you may have already noticed, most of the combustion products are toxic substances. Therefore, speaking of their classification, it will be correct to analyze the classification of toxic substances.
First of all, all toxic substances - hereinafter - OM - are divided into deadly, temporarily incapacitating and irritating. The former are divided into agents that affect the nervous system (Vi-X), asphyxiating (carbon monoxide), boiling skin (mustard), and common poisonous (hydrogen cyanide). Examples of temporarily disabling OM can be attributed to B-Zet, and to annoying adamsite.
Volume
Now let's talk about those things that we must not forget about when talking about the products emitted during combustion.
The volume of combustion products is important and very useful information, which, for example, will help determine the level of danger of combustion of a substance. That is, knowing the volume of products, you can determine the amount of harmful compounds that make up the gases released (as you recall, most products are gases).
In order to calculate the desired volume, first of all, you need to know if there was an excess or lack of an oxidizing agent. If, for example, oxygen was in excess, then all the work comes down to compiling all the reaction equations. It should be remembered that fuel, in most cases, contains impurities. After that, according to the law of conservation of mass, the amount of the substance of all combustion products is calculated and, taking into account the temperature and pressure, according to the Mendeleev-Clapeyron formula, the volume itself is found. Of course, for a person who does not understand anything in chemistry, all of the above looks scary, but in fact there is nothing difficult, you just need to figure it out. You should not dwell on this in more detail, since the article is not about that. With a lack of oxygen, the complexity of the calculation increases - the reaction equations and the combustion products themselves change. In addition, more abbreviated formulas are now used, but for a start it is better to consider the presented method (if necessary) in order to understand the meaning of the calculations.
Poisoning
Some substances released into the atmosphere during the oxidation of fuel are toxic. Poisoning by combustion products is a very real threat not only in case of fire, but also in a car. In addition, inhalation or another way of getting some of them does not lead to an instant negative result, but will remind you of this after a while. For example, carcinogens behave this way.
Naturally, everyone needs to know the rules that prevent negative consequences. First of all, these are the rules of fire safety, that is, what every child is told from early childhood. But, for some reason, it often happens that both adults and children simply forget them.
The rules of first aid for poisoning are also likely to be familiar to many. But just in case: the most important thing is to take the poisoned person to fresh air, that is, to fence off further toxins in his body. But you also need to remember that there are methods of protection against products of combustion of the respiratory system, body surface. This is a protective suit for firefighters, gas masks, oxygen masks.
Protection against toxic combustion products is very important.
Personal use of a person
The moment when people learned to use fire for their own purposes, was undoubtedly a turning point in the development of all mankind. For example, one of its most important products - heat and light - was used (and is still used) by a person in cooking, lighting and warming in cold weather. In ancient times, coal was used as a drawing tool, and now, for example, as a medicine (activated carbon). The fact that sulfur oxide is used in the preparation of the acid has also been noted, phosphorus oxide is also used in the same way.
Output
It is worth noting that everything described here is only general information presented to familiarize yourself with questions about combustion products.
I would like to say that compliance with safety rules and prudent handling of both the combustion process itself and its products will make it possible to use them to good use.