How to Evaluate an Odor in Your Building


What’s that smell? Is it dangerous? Should I be concerned? Odor evaluations can be one of the most difficult indoor environmental quality (IEQ) investigations to perform. Odors are also an issue that can quickly escalate from murmuring to a major problem for building owners and management.

Approached correctly, though, an odor evaluation can show building occupants you are listening to their concerns and are actively taking measures to protect them. Approached incorrectly, odors can tarnish the confidence occupants place in you, your business, and the environmental health of your building.

So, whether you take the proper steps to curb an odor problem as soon as the complaints begin or you wait until your occupants demand an investigation — that’s up to you, but your decision will quite likely affect the outcome of the situation.

When you’re ready to get started, here’s a brief description of how FACS IEQ experts approach an odor evaluation. You can use it as a guide to your own odor evaluation or as a way to help pave the way for the IEQ professional you hire.

The Dimensions of Odor

Odors differ according to a number of factors. Let’s first consider the dimensions you’ll want to examine in your odor evaluation process.

Detectability – The odor threshold is the lowest concentration of odorant that will elicit a sensory response in individuals. Odor threshold values are not fixed physiological parameters or physical constants, they are statistical points representing the best estimated value from a group of individual responses. Is the smell evident to all, or do some detect the odor while others do not?

Character – What does the substance smell like? We associate smells with something familiar to us according to their character. Some odors remind people of a wet dog, others say the odor smells like a dead fish, or maybe the odor you are investigating seems chemical in nature. Odor perception can vary with intensity, and the character reported may differ from source to source.

Hedonic tone – This term refers to the relative pleasantness or unpleasantness of an odor. Perception of hedonic tone is influenced by subjective experience, frequency of occurrence, odor character, odor intensity, and odor duration. Perceptions can differ widely from person to person and are influenced by personal factors such as emotions, previous experience, and other individual experiences.

Once you’ve defined the dimensions of odor you are a step closer to evaluating the source and potential health impact of building occupants. Odors are present in most environments. Your job is to determine whether the odor is hazardous to health, where it is coming from, and how it can be mitigated.

Odor Issues to Investigate

You want to find the source of the odor and develop a plan to mitigate it — that is most often your primary set of goals. But there are other issues you will want to investigate along the way to accomplishing those tasks.

Pathway: What are the possible routes the odor is taking to get from the point of origin to the area of complaint? There are times when an odor source can’t be removed, but it is possible to stop the odor from gaining access to the occupants of your building.

Exposure: At what concentration are the odorous compounds present in the environment? What is considered “typical background levels” for those compounds. What is considered a health hazard? Comparing laboratory results to occupational exposure limits may not be appropriate when evaluating an odor complaint, as exposure limits are based on values which indicate levels of exposure that are considered to be safe (health-based) and do not take into consideration general comfort. For example, a plumber may be exposed to hydrogen sulfide (major constituent of sewer gas; described as a rotten egg odor) on a daily basis, however, an office employee working in a cubicle would not want to or expect to similarly smell the rotten egg while at work.

Health effects: Are occupants experiencing health issues from the odor? Are they getting headaches, becoming nauseous, or finding it difficult to breathe? Are all occupants experiencing the same symptoms, or do the reported health effects vary in nature or severity?

An odor evaluation is most often a reverse-engineering process. You begin with the results, then trace back towards the source of the odor. Once you’ve determined the issues involved you may be able to rule out many possible sources and gain clues to the most probable cause.

Steps to Odor Investigation

Once you’ve categorized the dimensions of the odor and the issues it is apparently causing, you’re ready to begin a step-by-step investigation. Below is the standard sequence FACS experts follow when performing an odor evaluation.

1. Develop a building history and background information. Are the current complaints new, or have there been prior odor problems in the building? If prior issues are found, how frequently do they occur, and are the dimensions and reported health effects arising from the odor similar to the problem now under investigation? Has anything recently changed or occurred in the building (e.g., water intrusion event), that may be attributed to the odors experienced.

2. Inspect the area and speak with the people. Walk through the affected spaces and speak with the occupants. Trace likely pathways to see if one or more of them arrive at a potential source. Were there changes to cleaning products used, has new equipment been installed, has the HVAC system been properly maintained? These and other observations will provide the data you need to find the source and mitigate it.

3. Formulate a hypothesis. Carefully consider the information you have collected. Given the odor dimensions, the issues you have evaluated, the building history, the complaints the odor is generating, and your onsite sensory (visual and olfactory) inspection, what is the likely source and how can it be mitigated?

4. Test your hypothesis. This step may require you to take samples of the probable source for laboratory analysis. There are times when you can easily remove a source from the premises to see if the odor begins to diminish, but there are other times when the removal of a potential source is quite complicated. Testing can be critical. You may mistakenly attribute the odor to something that isn’t the real source at all. That puts you right back to the beginning of your investigation.

This is most often the point where FACS consultants are asked to join the effort. Not only is it difficult to sample for odors on your own, but the experience FACS environmental health experts bring to the problem often allow us to get to a solution quicker and with a more favorable outcome for all concerned.

FACS Can Help With Odor Evaluations

In some cases there is a simple source and solution. In one case, for instance, the maintenance team at a high school couldn’t determine the source of a foul odor. It didn’t take long for FACS to find the source, though: A senior prank included placing dead fish inside the ventilation system.

Odors can cause major concerns within the affected group of people. When you listen carefully to their complaints and take quick action to address them, you gain the trust and appreciation of building occupants. They want to know that you care about them, and odor evaluations are one way to assure them you are serious about their comfort.

If you choose to investigate an odor on your own, keep records of the steps you take and be sure to keep occupants informed about what you are doing to track down and get rid of the odor. If you decide you need help from indoor environment quality specialists — whether to save time, solve a seemingly unsolvable issue, or to demonstrate your concern to your occupants — remember that public health is always at the top of the list for building owners. Call FACS at (888) 711-9998. We can help.