Sampling Location

Brief:

In Hong Kong, the Environmental Protection Department (HKEPD) has launched an indoor air quality (IAQ) certification scheme to promote an acceptable IAQ in workplaces. However, the associated uncertainties and measurement efforts have not been detailed for practical measurement in indoor spaces. We choose indoor carbon dioxide (CO₂) concentration as an indicator of the indoor air quality to investigate the probable errors and measurement efforts in different sampling schemes regarding the sampling point density. In particular, a one-year measurement for sample-spatial average indoor CO₂ concentration at 17 sampling locations in a typical large office (floor area = 1200 m²) has been used to evaluate the probable errors of the sample-spatial average concentrations using different sampling point densities of random choice of sampling locations. The uncertainties of professional choice of ‘representative’ sampling locations for general indoor air quality (IAQ) assessment are also investigated from the perspective of probable errors deviated from the sample-spatial average pollutant concentration of an indoor environment. Associations between the professional choices of the sampling locations and attributes of the assessors were examined to quantify the uncertainties of the IAQ assessment results. Comparing with the random choices, the assessment accuracy with the expert choices would be significantly improved for coarse sampling point densities at certain engineering acceptable error limits. It was reported that the location choices and assessment accuracy would be significantly influenced by the academic background of the assessors. An assessor group with higher academic level would make a choice leaning towards more accurate assessment results.

Further information:

How many points I need to measured?

Mui KW, Wong LT, Ho WL, 2006. Evaluation on sampling point densities for assessing indoor air quality, Building and Environment 41(11) 1515-1521.

Do we require professional training in selecting the location?

Hui PS, Wong LT,Mui KW, 2007. Evaluation of professional choice of sampling locations for indoor air quality assessment, Building and Environment 42(8) 2900-2907.