Odour Testing

Nuisance odours or bad smells are a common cause of indoor air quality complaints, and can be one of the most challenging problems to solve.


Where is that smell coming from?


The source of an odour can be difficult to identify particularly within indoor environments. There are many potential sources and air-flow paths which can exist within a building. Building features such as stairwells, lift and service shafts, the heating ventilation and air-conditioning system (HVAC) and other wall and ceiling penetrations provide routes for the dissemination of odours. Common sources of nuisance odours within the built environment include:


  • sewer connections
  • drinking water, grey water  and black water systems
  • rubbish, solid waste or waste treatment systems
  • fires, floods and other disasters
  • carpet, paint and surface coatings
  • solvents and cleaning chemicals
  • furniture and fittings
  • building materials
  • vehicles and other combustion sources
  • rodents and other animals and;
  • fugitive emissions from neighbours


What is that smell?


Our perception of odour is unique to us and varies for a range of reasons including; age, gender, health status, pregnancy and genetic differences.


Our memory of past exposures to similar odours is individual and our opinions of different odours are imprinted in our minds from a young age. These odour memories impact the way new odours are perceived.


When strange odours appear in the work environment people’s perception of the smell are often very different. What is a pleasant or benign smell to one may cause alarm or discomfort to another. 


Location is also a factor, an odour which is acceptable in a gym or a car park may be considered offensive in our home or workplace. The smell of roasting coffee is generally considered a pleasant odour but perhaps not if it’s found in your bedroom.


Can you smell that?


The point at which an odour becomes a nuisance odour is specific to each person and depends on the frequency, intensity, duration, offensiveness and location of the odour.


Frequently an odour is noticeable to only a few occupants and they may have different opinions about the identity of the smell. Constant exposure to an odour may cause the receptors in the nose that detect smells to become odour fatigued, and often over time Smells that were initially unpleasant are no longer obvious.


Depending on its source, the odour may appear intermittently, often presenting a few times a day with no particular pattern.


Nuisance odour or work health and safety risk?


The primary concern of employers and building managers is whether the nuisance odour presents a work health and safety risk. The presence of an odour does not necessarily mean that the compound(s) responsible for the odour represents a health hazard. An example is ethyl mercaptan, a common volatile organic compound (VOC), which has an odour threshold (the point at which an odour is detectable by 50% of the population) of 1ppb, well below the exposure limit of 100ppb.


How is odour testing carried out?


Odour concentration is measured using a dynamic olfactometer by a group of trained panelists. The other attributes of odour that are assessed are:


  • Odour intensity - the perceived strength of an odour
  • Hedonic tone - a subjective rating of the “unpleasantness” of an odour
  • Odour character/quality - critical in assessing the nature or source of an odour. May include categories such as: floral/fragrant, fruity, vegetable, earthy, fishy, offensive, chemical, medicinal.
  • Odour perception and irritation is also measured.


Intensity and concentration are related by the Weber-Fechner Law (a log-linear function).


For more information about nuisance odour or to request a consultation, please call us on 1800 878 262 or email admin@bell-labs.com.au.