I commonly hear the phrase, “I smell something” when initially assessing a work place. Although the nose can be a great tool, you would not want to rely on this method for determining if you’re employees are safe.

The American Industrial Hygiene Association (AIHA) produces a reference book titled, “Odor Thresholds for Chemicals with Established Occupational Health Standards”.  Of the 680 compounds with recommended limits, this book lists approximately 182 chemicals. So, although, we can’t smell everything, it might be good to know which chemicals we can smell and at what level.

Odor has four dimensions:

  1. Detectability. Each individual can detect different levels, but let’s leave that out. For the most part there is a minimum level that it is detectable; it is considered saturated at this level and you can tell what it is.
  2. Intensity. This is it’s strength. A good cook can tell when their pot roast is done by the intensity of the odor.
  3. Character. What does it smell like? We all associate smells with something such as, a wet dog, a fish, or a blooming flower.
  4. Foulness (Hedonic tone). This is your perceived smell. Rotten eggs are usually not a pleasant odor. However, the moldy smell from a locker room might be considered bad, but the mold odor from cheese might be more pleasant.

The best situation is to have an odor threshold well below any establish limits for the chemical you are using. An example of this is acetone (2-propanone). Acetone is found in many cleaners and paints and is detectable to the nose at around 62-100 parts per million (ppm) or 0.01%. The permissible exposure limit for acetone is 1000 ppm (or 1%).  This would be a chemical with good warning properties.

Unfortunately your nose isn’t always as good at detecting harmful levels. For example, benzene (found in gasoline and other chemicals) has an odor around 60-90 ppm (0.009%), while the exposure limit for benzene is only 10 ppm (0.001%). This means that if you can smell it, you have already exceeded the acceptable limits.

Another popular chemical without good warning properties is diisocyanates. These are commonly found in paint systems at auto body repair facilities. These types of chemicals diphenylmethan-diisocyanane (MDI),  Hexamethylene diisocyanate (HDI) and toluene diisocyanate (TDI) have virtually no smell, their exposure limits are very low (around 0.005 ppm), and, to make matters worse, they are hazardous to your health.

So, my advice for those seeking to know more: explore the material safety data sheets (MSDS) that you use. Look in Section 2 under Hazardous Materials. Know these chemicals. Do you know the employee’s exposure levels while it is in use? Do you know their respective exposure limits? Are you wearing a respirator? Do you know the odor threshold?