Many people know that death during a fire occurs more often due to poisoning by combustion products than from thermal exposure. But you can get poisoned not only during a fire, but also in everyday life. The question arises as to what types of combustion products exist and under what conditions are they formed? Let's try to figure it out.
What is combustion and its product?
There are three things you can look at endlessly: how water flows, how other people work, and, of course, how fire burns…
Combustion is a physical and chemical 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. This process involves a substance or a mixture of substances that burn - reducing agents, as well as an oxidizing agent. Most often this role belongs to oxygen. Combustion 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 are 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, the combustion products are smoke, ash, soot, emitted gases, including exhaust gases. 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 released during combustion: carbon oxides
There are two oxides of carbon: CO2 and CO. The first is called carbon dioxide (carbon dioxide, carbon monoxide (IV)), as 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 of oxygen during combustion. In addition, carbon dioxide is released by living beings during respiration. 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 poisonous gas, in the molecule of which carbon is in the +2 oxidation state. That is why this compound can "burn out", that is, continue to react with oxygen: CO+O2=CO2. Homea dangerous feature of this oxide is its incredibly large, in comparison with oxygen, ability to attach to red blood cells. Erythrocytes 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 monoxides are colorless and odorless.
Water
The well-known water - H2O - is also released during combustion. At the combustion temperature, the products are released in the form of gas. And water is like steam. Water is a combustion product of methane gas - CH4. 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.
Sulfide gas, hydrogen sulfide
Sulfide gas is also an oxide, but this time sulfur is SO2. It has a large number of names: sulfur dioxide, sulfur dioxide, sulfur dioxide, sulfur oxide (IV). This combustion product is a colorless gas, with a pungent smell of an ignited 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 (Н2S).
When it comes into contact with the mucous membranes of the eyes, nose or mouth of a person, dioxide easily reacts with water, forming sulfurous acid, which easily decomposes back, butat the same time, it manages to irritate the receptors, provoke inflammatory processes in the respiratory tract: SO3. This is due to the toxicity of the combustion product of sulfur. Sulfur dioxide, like carbon monoxide, can burn - oxidize to SO3. But this happens at very high temperatures. This property is used in the production of sulfuric acid at the plant, as SO3 reacts with water to form H2SO4.
But hydrogen sulfide is released during the thermal decomposition of some compounds. This gas is also poisonous, with a characteristic smell of rotten eggs.
Hydrogen cyanide
Then Himmler clenched his jaw, bit through an ampoule of potassium cyanide and died a few seconds later.
Potassium cyanide - the strongest poison - a s alt 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 poisonous, even a small concentration in the air - 0.01 percent - is fatal. A distinctive feature of the acid is the characteristic smell of bitter almonds. Appetizing, isn't it?
But hydrocyanic acid has one "zest" - it can be poisoned not only by inhaling directly with the respiratory system, but also through the skin. So it will not work to protect yourself only with a gas mask.
Acrolein
Propenal,acrolein, acrylaldehyde - all these are the names of one substance, unsaturated acrylic acid aldehyde: 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 vapors get on 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 present in the atmosphere in large quantities. Nitrogen can be an example of a combustion product of amines. But during thermal decomposition, for example, ammonium s alts, and in some cases 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 that are brown in color and extremely toxic.
Ashes, ash, soot, soot, coal
Soot, or soot - the remains of carbon that has not reacted for various reasons. Soot is also called amphoteric carbon.
Ash, or ashes - small particles of inorganic s alts that have not burned or decomposed at the combustion temperature. When the fuel burns out, these micro-compounds become suspended or accumulate at the bottom.
And coal is a product of incomplete combustionwood, that is, its unburned remains, but still capable of burning.
Of course, these are not all compounds that will be released during the combustion of certain substances. To list them all is unrealistic, and it is not necessary, because other substances are released in negligible amounts, and only when certain compounds are oxidized.
Other mixes: smoke
Stars, forest, guitar… What could be more romantic? And one of the most important attributes is missing - a fire and a wisp of smoke above it. What is smoke?
Smoke is a kind of mixture that consists of gas and particles suspended in it. Water vapor, carbon monoxide and carbon dioxide, and others act as gas. And solid particles are ash and just unburned residues.
Exhaust
Most modern cars run on an internal combustion engine, that is, for movement, the energy obtained from the combustion of fuel is used. Most often it is gasoline and other petroleum products. But when burned, a large amount of waste is released into the atmosphere. This is the exhaust gases. They are released into the atmosphere in the form of smoke from car exhaust pipes.
Most of their volume is occupied by 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, meaning they increase the risk of developing cancer.
Features of products of complete oxidation (in this case, combustion) of substances and mixtures: paper, dry grass
WhenWhen paper is burned, carbon dioxide and water are also released, and when there is a lack of oxygen, carbon monoxide is released. In addition, paper contains adhesives that can be released and concentrated, and resins.
The same situation occurs when burning hay, only without adhesives and resin. In both cases, the smoke is white with a yellow tint, with a specific smell.
Wood - firewood, boards
Wood consists of organic matter (including sulfur and nitrogen) and a small amount of mineral s alts. Therefore, when it is completely burned, carbon dioxide, water, nitrogen and sulfur dioxide are released; gray, and sometimes black smoke with a tarry smell, ash is formed.
Sulfur and nitrogen compounds
We have already talked about toxicity, combustion products of these substances. It is also worth noting that when sulfur is burned, smoke is emitted with a grayish-gray color and a pungent smell of sulfur dioxide (since it is sulfur dioxide that is emitted); and when burning nitrogenous and other nitrogen-containing substances, it is yellow-brown, with an irritating odor (but smoke does not always appear).
Metals
When metals are burned, oxides, peroxides or superoxides of these metals are formed. In addition, if the metal contained some organic or inorganic impurities, then combustion products of these impurities are formed.
But magnesium has a combustion feature, since it burns not only in oxygen, like other metals, but also in carbon dioxide, forming carbon and magnesium oxide: 2 Mg+CO2=C+2MgO. The smoke is white, odorless.
Phosphorus
When burning phosphorus, white smoke is emitted that smells like garlic. This produces phosphorus oxide.
Rubber
And, of course, tires. The smoke from burning rubber is black, due to the large amount of soot. In addition, combustion products of organic substances and sulfur oxide are released, and thanks to it, the smoke acquires a sulfurous smell. Heavy metals, furan and other toxic compounds are also released.
Classification of poisonous substances
As you may have noticed, most combustion products are poisonous. Therefore, speaking about their classification, it would be correct to analyze the classification of toxic substances.
First of all, all toxic substances - hereinafter OV - are divided into deadly, temporarily incapacitating and irritating. The former are divided into agents affecting the nervous system (Vi-X), asphyxiating (carbon monoxide), skin-blistering (mustard gas) and generally toxic (hydrogen cyanide). Examples of temporarily incapacitating agents include B-Zet, and annoying - adamsite.
Volume
Now let's talk about those things that should not be forgotten when talking about 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 particular substance. That is, knowing the volume of products, you can determine the amount of harmful compounds that make up the released gases (as you remember, most products are gases).
To calculate the desired volume, firstturn you need to know whether there was an excess or lack of an oxidizing agent. If, for example, oxygen was contained 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 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 knows nothing about chemistry, all of the above looks scary, but in fact there is nothing difficult, you just need to figure it out. It is not worth dwelling 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 it is better to start with the presented method (if necessary) in order to understand the meaning of the calculations.
Poisoning
Some substances emitted 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, inhaling or otherwise ingesting some of them does not lead to an instant negative result, but will remind you of this after a while. For example, this is how carcinogens behave.
Of course, everyone needs to know the rules to prevent negative consequences. First of all, these are fire safety rules, that is, what every child is told from early childhood. But, for some reason, it often happens thatadults and kids just forget them.
The rules for first aid in case of poisoning are also most likely 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 from entering his body. But you also need to remember that there are methods of protection against the products of combustion of the respiratory organs, the surface of the body. This is a protective suit for firefighters, gas masks, oxygen masks.
Protection from toxic combustion products is very important.
Private 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, some of its most important products - heat and light - were used (and are still used) by man in cooking, lighting and warming in cold weather. Coal in ancient times was used as a drawing tool, and now, for example, as a medicine (activated carbon). The use of sulfur oxide in the preparation of acid has also been noted, and so is phosphorus oxide.
Conclusion
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 reasonable handling of both the combustion process itself and its products will allow them to be used to good use.
