Odor and the Science of Olfaction

Introduction
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

An examination of the ins and outs of removing odors from your home must commence with the basics. An initial discussion of odor and the science of olfaction is vital. What this means is that you must have an essential understanding of how odor is created in the first instance and how smells are processed by your nose and brain.

The life of a human being is significantly dependent upon the functioning or operation of the five physical senses. From an early age, a youngster identifies these senses:

  • Seeing
  • Hearing
  • Touching
  • Tasting
  • Smelling

Arguably, the sense that receives the least amount of discussion and consideration is that of smell. Indeed, for most people in most situations, the total extent of contemplation of the sense of smell is brief, succinct, and simple:

“Something smells good”

“Something smells bad”

In reality, the sense of smell is a highly complicated process.

Overview of Science of the Sense of Smell

As noted at the start of this chapter, a basic understanding about the scientific mechanics of the sense of smell is vital when it comes to understanding odors and how to abate them. The sense of smell has received something of a short shrift from scientists and researchers. Only fairly recently has olfaction and odor more significantly become the focus of research.

Olfaction is the medical term for the chemoreception or chemical reaction that creates a person’s sense of smell. In layperson’s terms, it is the manner in which the nose and brain identify a smell.

A person’s nose is the organ that is responsible for the sense of smell or olfaction. The inside of the nose is lined with mucous membranes. These mucous membranes have smell receptors. In turn, these receptors are connected to what is known as the olfactory nerve. The olfactory nerve conveys information from the receptors to various parts of the brain to interpret an odor.

The smell receptors receive molecules from vapors arising from different substances. For example, a rose emits certain vapors, containing unique molecules, that interact with the smell receptors in an individual’s nose.

The Scientific Nature of Odors: An Examination of the Properties of Odorous Molecules

A moment ago, a discussion was presented about how odors, or odorous molecules, interact with the human body. Armed with this primary information, you must also understand the inherent properties associated with odors themselves, technically known as odorous molecules.

In order for a substance to have a detectable odor, it must be water soluble. Two essential elements must be present in order for a molecule to be able to “convey an odor” through the biological process of olfaction. First, in order for a molecule to be capable of transferring an odor it must be what scientifically is known as volatile. Volatile means that a molecule is capable of being vaporized at normal temperatures and air pressures.

Simply put, a molecule must be capable of going from the source of the odor to a person’s olfactory system – to an individual’s nose. A molecule must be capable of vaporization in order to be inhaled.

Second, the molecule itself must contain an element of moisture or dampness. A truly infinitesimal amount of moisture or dampness suffices. The receptor in a person’s nose necessitate this moisture within a molecule to activate. In addition, a receptor requires a molecule to contain one or another of three other components in order to trigger the process of olfaction:

  • Lipids
  • Oils
  • Fats

The manner in which a molecule fits into a receptor dictates the manner in which information about the source, quality, and nature of an odor is transmitted to the brain. The moment a molecule lodges into a receptor, data about its size, shape, and other aspects is instantly conveyed to the olfactory lobe for basic interpretation and then onward to the brain for processing.

Theories about How Olfactory Receptors in the Nose Function

As mentioned earlier in this chapter, research into olfaction is somewhat in its infancy. As a result, at the present time there are only a trio of theories about how olfactory receptors in a person’s nose function or operate. These are:

  • Vibration Theory
  • Shape Theory
  • Odotope Theory

Vibration Theory

The vibration theory postulates that a receptor reacts to an odorous molecule by detecting its unique vibration and frequency. The vibration and frequency trigger the electric pulse that travels to the olfactory lobe for processing.

Shape Theory

Proponents of the shape theory argue that odorous molecules connect with or lock into receptors based solely on their unique shape. The theory is based on the contention that the unique shape ultimate triggers a specific smell.

Odotope Theory

The odotope theory is derivative of the shape theory. Under this hypothesis, individual receptors garner small bits of data from each molecule. That data is then assembled after transmission to the brain, rather like piecing together a puzzle, to create the overall sensation of a specific odor, smell, or scent.

Odor Characteristics

Ascertaining the characteristics of odor is largely a subjective process. Because of the manner in which odorous molecules are processed by an individual, the response to an odor will be at least slightly different from one person to another.

The smell receptors in person’s nose are sensitive to seven specific types of sensations. These are:

  • Musk
  • Flower
  • Mint
  • Ether
  • Camphor
  • Acrid
  • Putrid

A person considering this list of “taste sensations” might initially conclude that it cannot possibly be complete. Human experience underscores that a person confronts a myriad of different odors on any given day that do not fit neatly into one or another of these seven categories. Scientifically, a particular substance can emit a vapor that activates multiple types of smell-related sensations simultaneously, which result in the brain interpreting a unique odor.

Keep in mind that the human sense of taste involves even fewer sensations:

  • Savoriness
  • Sweetness
  • Bitterness
  • Saltiness
  • Sourness

Even with only five points on the taste spectrum, the blended response to particular sensations result in a myriad of tastes experienced by a person. The sense of smell operates in the same manner with a multitude of individual odors built upon seven more specific olfactory sensations.

A key way in which an odor is characterized is via intensity. Researchers and odor remediation specialists utilize a six-point rating scale. The scale is subjective and reminiscent of the 10-level pain scale often used by medical professionals. The odor intensity scale is:

  • Zero (0) – no odor
  • One (1) – barely perceptible odor level.
  • Two (2) – distinct odor
  • Three (3) – strong odor
  • Four (4) – very strong odor
  • Five (5) – overpowering odor

Due to the subjectivity of associated with identifying the nature and intensity of odor, a third party may need to become involved in the assessment, including a remediation specialist. For example, a homeowner might have become acclimated to an odor and cannot readily judge its presence, let alone its intensity.

Some people are incapable of identifying certain odors, either because of physical or psychological reasons. Indeed, some people have no sense of smell at all and are known as anosmatic. A person can be anosmatic temporarily or permanently, and have this condition for a number of reasons including:

  • Colds
  • Viruses
  • Allergies
  • Traumatic brain injury

Now that you are armed with a basic, essential understanding of odor and the science of olfaction, in the next chapter you are presented with a discussion of primary odor sources.

Next: Chapter 2: Exploration of the Sources of Odor