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When to Sample VOCs

Sampling for VOCs should only be done after source elimination has been considered as a first step. If this is not possible, or too expensive, sampling could then be considered. The source-pathway-receptor relationship will have characteristics that will influence the sampling method and duration. Table 2-5 shows how VOC sampling can be tailored to suit various complaint patterns.

If the timing of a source is well known it may be used to define the source-pathway-receptor relationship and possibly eliminate or reduce the amount of VOC sampling required. For example, if odour or health complaints can be correlated with building conditions, occupant/neighboring activities, weather, or ventilation system status, then it may be possible to determine the source or pathway, and mitigate the problem without sampling or to adjust the sampling program.

Table 2-5 Complaint patterns and sampling methodology

Description

Sampling / Analysis Considerations

Short-term

Complaints that occur at specific times should result in sampling that occurs at those times. To allow for pre-concentration prior to analysis short-duration, whole-air sampling followed by VOC characterization may be appropriate.

Continuous

When complaints are received continuously, short duration sampling followed by VOC characterization (e.g., Austen Method (AM) 1.2) would be appropriate.

Seasonal

Complaints that occur seasonally should be assessed by comparing VOC profiles for both the complaint and non-complaint periods.

Periodic

Complaints that occur periodically should result in sampling that occurs at those times, sampling duration should be appropriate for event duration.

Erratic

Erratic complaints are most problematic and may require sampling close to com- plaint areas and providing a means for affected people to quickly advise of reoccur- rences of symptoms.

The duration of sampling should provide data that it is representative and meaningful. How the data will be interpreted should be considered. Timing factors may also be defined by legislation such as determi- ning short-term exposure or time weighted average exposure for workers. Where timing is not defined by legislation, occupants should be interviewed or asked to complete a questionnaire to gain an unders- tanding of when exposure may be occurring. It is important to note that complainants may not always be objective when providing information.

For more information on VOC sampling strategies and methods, go to:  http://iaqforum.ca/wp-content/uploads/2012/11/Mod2_VOC.pdf

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