Chapter 1: Odor and the Science of Olfaction
Chapter 2: Exploration of the Sources of Odor
Chapter 3: The Interrelationship Between Microorganisms and Odor
Chapter 4: Effective Odor Detection Techniques
Chapter 5: Process of Deodorization
Chapter 6: Process of Oxidation
Chapter 7: Process of Enzymatic Action
Chapter 8: Process of Chemical Deodorization
Chapter 9: Process of Sealing
Chapter 10: Deodorization Equipment and Supplies
Chapter 11: Remediating Protein and Chemical Odors
Chapter 12: Death Scene Restoration

Various university courses are devoted to studying microorganisms and microbiology. Many astute academics consider these courses to be some of the most complicated and challenging offered on both the undergraduate and post-graduate levels. Nothing in this book is designed to supplant the painstaking endeavors associated with such university pursuits. Rather, this chapter is intended to aid you in coming to an essential and necessary understanding of the interrelationship between microorganisms and odor.

The effective remediation of odors necessitates a basic understanding of the association between microorganisms and certain types of odors. Absent this appreciation of the connection, an individual is not positioned to be able to effectively eliminate certain odors. In fact, a lack of understanding of this interconnection can actually result in not only a failure to remediate an odor but making it far worse. Moreover, depending on the microorganisms at issue, an individual attempting remediation could end up exposing himself to a hazardous pathogen that can result in severe or even deadly illness.

Types of Microorganisms

Two types of microorganisms are the subject of considerations when it comes to odors. These are bacteria and fungi.

Deodorization oftentimes is associated with a broader effort at biohazard remediation. Biohazard cleanup will be concerned with other pathogens beyond these two microorganisms. Specifically, biohazard cleanup or remediation will also involve the eradication of viruses as well as addressing bacteria and possible fungi.

Technically speaking, viruses should not be classified as microorganisms because they are not living as is the case with bacteria or fungi. Nevertheless, viruses sometimes are lumped together with true microorganisms. Noting that, viruses are not direct contributors to the genesis of any type of odor.

A living being like a human or a pet cat or dog is themselves home to a myriad of microorganisms, specifically bacteria. There are more microorganisms living on a human’s skin at any time than there are people on the planet. Moreover, within a human’s body, there are thousand-times more microorganisms alive than there are people populating Earth.

Overview of Bacteria

Bacteria are defined as being microscopic, single-celled organisms. They exist by the millions virtually anywhere, including inside as well as outside other living organisms. For example, bacteria can be found everywhere from in soil to the insides of cats, dogs, and humans.

Most bacteria serve a beneficial purpose. For example, with regularity, you may have heard reference to “good bacteria,” specifically bacteria in your “gut” that aids in digestion.

With that said, there are also “bad bacteria,’ microorganisms capable of causing serious or even fatal diseases in humans. Examples of diseases caused by bacteria include:

  • Urinary tract infections
  • Strep throat
  • Tuberculosis
  • MRSA

There are types of bacteria that cause diseases in other types of mammals, including cats and dogs.

Using humans as an example, good bacteria that live within the body include:

  • Lactobacillus Acidophilus
  • Bifidobacterium Bifidum
  • Streptococcus Thermophilus
  • Bacillus Coagulans

Classes of Bacteria

Two primary classes of bacteria exist:

  • Autotrophic
  • Heterotrophic

Autotrophic bacteria live on inorganic matter. Heterotrophic bacteria live on organic matter. Some heterotrophic bacteria can cause disease.

Heterotrophic bacteria can live in a mammal’s body, including the body of a human, cat, or dog. These bacteria rely on nutrients being provided through the blood system. When an animal dies, the bacteria then turns to the organs of the body itself for nutrition. The act of the bacteria “consuming” the body itself is at the heart of the decomposition process. Death, decay, and decomposition are discussed in greater detail in a moment.

Situations Involving Bacteria Most Commonly Requiring Remediation

There are two categories of odors most often confronted in a residential situation. These are:

  • Pet Odors
  • Death, decay, and purification

Each of these most common odors requiring remediation is discussed in detail.

Pet Odors

There are two primary sources of pet odors that require remediation, elimination of cleanup. The remediation process is discussed in a future article.

These are:

  • Pet urine (usually cats or dogs)
  • Odors arising from pet fur or hair, oils, and other secretions

The intensity of an odor, as well as other qualities, depends on the animal or pet. For example, cats have more ammonia in their urine whereas dogs have urine that is more sulfur-based. Bacteria are involved in the generation of pet odors.

Death, Decay, and Putrefaction

You can face odors associated with what is classified as death, decay, and putrefaction in three primary ways:

  • Food spoilage, including refrigerator or freezer failure
  • Death of small animals, including mice, pets, etc.
  • Death of larger living beings, like humans

As with pet odors, bacteria are involved in the generation of putrid smells associated with death, decay, and putrefaction. Various strategies to remediate odors are delineated in detail in the final chapters of this book.

Requirements for Living Bacteria

As is the case with any living organism, bacteria have certain requirements in order to survive. These are:

  • Nutrients
  • Moisture
  • Oxygen
  • Temperature


Nearly all bacteria require nitrogen and carbon in order to survive and grow. Carbon is derived from:

  • Fats
  • Proteins
  • Carbohydrates

Nitrogen Is Derived From:

  • Nitrates
  • Urea
  • Amino acids

Finally, an array of inorganic salts are also necessary nutrients for bacteria.


Moisture is indispensable for bacterial activity. Water is an ideal medium which allows bacteria the ability to feed and digest waste material. This permits bacteria the ability to not only intake nourishment but also reproduce and multiply. Moisture plays a crucial role in the creation and enhancement of odor. As moisture increases bacterial action, it enhances odors proportionally.


There are two types of bacteria classifications when it comes to an oxygen requirement:

  • Aerobic
  • Anaerobic

Aerobic bacteria require the presence of atmospheric or free oxygen. These bacteria are associated with the breakdown of urine and result in the foul odors associated with that substance.

Anaerobic bacteria do not require the presence of atmospheric or free oxygen. These bacteria are associated with the decomposition process and result in the most offensive odor levels possible.


Bacteria are relatively hearty. Bacteria can live and replicate in temperatures that range from 33 to 119 degrees Fahrenheit. With that said, bacteria thrive at temperatures between 60 to 85 degrees Fahrenheit, the temperature zone humans, and many other animals prefer.

Odor molecules are more readily detectable in the temperature zone preferred by bacteria. This is because warm air contains more moisture, which is crucial to convey vaporized molecules to an olfactory system.

A Look at Mold

In discussing the interrelationship between microorganisms and odor, reference must also be made to fungi, specifically mold. Mold is evidenced by odors that oftentimes are described as:

  • Moldy
  • Musty
  • Mildew
  • Earthy

These vapors, which result in odors, are created as a byproduct of the action of mold feeding and growing.

Mold can start from a single spore that is somehow conveyed into a residence from out of doors. A mold spore can be carried in on clothing or pet fur and in a number of other ways.

Mold is capable of growing nearly anywhere in which the following conditions are found to exist:

  • Moisture
  • Temperature between 68 and 85 degrees Fahrenheit
  • A lack of air circulation
  • Organic food source

Molds breakdown their food source via enzyme digestion in a manner like bacteria. As mentioned a moment ago, this process results not only in the nourishment of the mold but in the release of vapors that result in unpleasant odors.

With this general overview of the interrelationship between microorganisms and odor in hand, we now turn to a consideration of strategies that can be utilized to detect and identify the source of odors. As referenced in a previous article, pinpointing the source of an odor may not always be easy. Therefore, a homeowner, as well as a professional remediator, needs to be aware of different techniques that are effective at targeting the true source of a particular odor.

Next: Chapter 4: Effective Odor Detection Techniques


Emily Kil

Co-Owner of Eco Bear Biohazard Cleaning Company

Together with her husband, Emily Kil is co-owner of Eco Bear, a leading biohazard remediation company in Southern California. An experienced entrepreneur, Emily assisted in founding Eco Bear as a means of combining her business experience with her desire to provide assistance to people facing challenging circumstances. Emily regularly writes about her first-hand experiences providing services like biohazard cleanup, suicide cleanup, crime scene cleanup, unattended death cleanup, and other types of difficult remediations in homes and businesses.