When a person dies, the body immediately starts the decomposition process. During the different stages of decomposition, microbial communities create and release gases, which have certain odors.
So, although the body is dead, many organisms on and in the body remain alive, and it's these microorganisms that create the smell associated with death.
This article will discuss how these bacteria cause the smell of death, as well as what it smells like.
The Death Process
To understand why human bodies smell after dying, we first need to discuss what happens when a person dies.
A human being is considered dead when the heart stops beating. Although some organs, like the brain and skin, are alive for a period thereafter, the body can't function for long after the heart stops.
Let's look at what happens to human cadavers in the different stages of decomposition.
First stage: Fresh
This stage only lasts for a day or two. Nothing much happens at this point in terms of smell.
The body cools until it reaches room temperature, and the blood stops flowing and settles.
One thing that remains alive is the bacteria within the body, such as inside the intestines and pancreas.
Second stage: Putrefaction (bloating)
The bacteria start to break down their host - the human body - since the lack of flowing blood deprives them of needed nutrients.
This often starts in the pancreas, and, as these organs are broken down, bacteria move to other organs and parts of the body.
Within two to three days, the corpse will discolor and foul-smelling gases will be released as more parts of the body are decomposed. Gas trapped in the body causes bloating.
Many people liken the smell of death to that of rotting meat.
This smell is due to volatile organic compounds released by the bacteria as they spread.
Third stage: Active decay
During this stage, which lasts around 10 days, insect activity increases and maggots start breaking down tissues.
The dead body smell intensifies due to the ongoing release of organic compounds.
Fourth stage: Advanced decay
Advanced decay starts roughly a month after the person has died. Fermentation of the tissues occurs, which attracts more insects that further decompose the body.
Eventually, the corpse will turn green, then purple, and finally - if left for long enough - black, as the bacteria works through the decomposing human body.
Fifth stage: Skeletonization
This stage is the final step in the decomposition process.
The body is almost fully decomposed, with only the bones, hair, and skin remaining. There are no longer any gases being released; however, the death smell might still linger as it has soaked into the upholstery or items near the dead body.
The Compounds Behind The Smell Of Death
Bacteria break down the proteins in body tissues, which release volatile organic compounds into the air and are responsible for the smell of a decomposing body.
Here are the nine main compounds responsible for the recognizable scent of human remains:
Hydrogen sulfide: It has the smell of rotten eggs.
Putrescine: Has a putrid odor, likened to that of rotting flesh.
Cadaverine: Like putrescine, it also smells like rotting meat.
Skatole: It is linked to the feces of mammals. In lower concentrations, it can smell pleasant; however, this organic compound smells earthy and strong in high concentrations associated with human decomposition.
Indole: Smells earthy and fecal, similar to skatole. Can be compared to the odor of sewage.
Dimethyl disulfide: Smells like garlic and is known to attract blowflies.
Dimethyl trisulfide: Also smells like garlic.
Trimethylamine: Similar to ammonia, it has a fishy odor.
Methyl mercaptan: Released early in the decomposition process, it smells strong like eggs and cabbage.
The chemical compounds released depend on the stage of decomposition, the temperature, environmental conditions, and the types of microbial communities present in the decomposing body.
Organisms Responsible For Decomposition
The microorganisms found on a decomposing body that are responsible for the smell of death depend on:
The bacteria found in and on the body while alive
The stage of decomposition
The climate where the person died
The person's diet and genetic makeup
Bacterial interactions
Here are some of the most common decomposers responsible for the odors associated with death.
Bacteria
Bacteria are the main decomposers responsible for releasing odors.
Early decomposers: These bacteria are both aerobic and anaerobic. They break down proteins and carbohydrates, releasing mainly cadaverine and putrescine which contribute to the smell of death.
Late decomposers: The main late decomposing bacteria are staphylococcus. These common bacteria decompose the remaining tissues, including fatty acids and proteins. Staphylococcus along with pseudomonas contribute to a wide range of volatile organic compounds released during the later stages of decomposition.
Fungi
Bacteria are the main decomposers responsible for odors associated with human corpses; however, fungi, like mold, also play a crucial role.
Fungi break down complex molecules and cellulose.
Mold is not really associated with the smell of death; however, some do produce cadaveric volatile organic compounds that have an earthy or musty odor.
Insects
Blowflies are the most common insects associated with human decomposition. Although they are not directly linked to the smell of a dead body, the maggots introduce more bacteria to the corpse, speeding up the decomposition process.
Is The Smell Of Death Harmful?
The smell of dead bodies is unpleasant, to put it mildly.
However, the odor itself is not considered harmful, as the gases are not hazardous or carcinogenic.
What could be harmful to human health is the presence of bacteria and parasites at the scene of the death. These organisms can spread diseases when coming into contact with the living.
The main gases released during decomposition - cadaverine and putrescine - are only harmful in very large volumes in confined spaces, and are not really considered a health risk.
Similarly, other gases associated with death, like hydrogen sulfide, methane, and carbon dioxide, are only considered hazardous when massive volumes are released.
So, the odor profile of a dead body will not pose any risks to you, but the parasites and bacteria may.
How To Get Rid Of The Smell Of Death
All cadavers release odors, and these smells can seep into anything in the surrounding environment, including carpets, upholstery, and any porous objects.
Getting rid of the dead body smell is no easy task, which is why most people call in biohazard decontamination companies like Chore-ology to not only get rid of odors but also thoroughly clean and decontaminate the scene.
Here are some steps you can take to get rid of that rotten odor:
Ventilate: Open all the windows and doors to allow fresh air to ventilate the space. Fans can also be used to help clear the smelly air.
Clean the environment: This is where you need the experts to step in. A biohazard cleanup crew will wear protective equipment and use various chemicals and disinfectants to kill all the odor-causing bacteria.
Absorb odors: You can use odor absorbers, like a DIY mix of vinegar and baking soda in a bowl, to absorb any remaining smells.
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