There is a discrepancy in the manual within the methodology section ‘Representative sampling of indoor air’. Please refer to the below instead:
Sample of indoor air principles
- Representative sampling of indoor air is permitted where multiple homes on a site incorporate the same building products or material specification.
- Different home ‘groups’ found on site must be covered by the representative indoor air quality tests, the different ‘groups’ are distinguished by the size, type, layout or location of homes on a site. For example, 1-bed apartment, 2-bed mid-terrace, 3-bed semi-detached, or 4-bed detached must each be representatively sampled.
- The sample size should be sufficiently large to demonstrate consistent performance across groups of homes.
Sample strategy for developments
The sample size can be modified to suit the developments specific environment and design if recommended by the accredited organisation undertaking the sampling. In this case a suitable sampling strategy must be produced that outlines the different groups outlined above, the rate of sampling per group type and how the sampling strategy still meets the intended requirements of the issue.
Justification for the sample group types
The Formaldehyde and TVOC concentrations are predominantly influenced by emissions from internal finishes and fittings. The concentrations of the emissions will depend on the source volume, the source rate, the room volume and the ventilation rate. This can be different based on size, type and layout of the building. In addition, the location of the homes should be taken into account as post-construction testing can be influenced by when the home was completed, with homes finished first having a lower emission rate, by external emission factors such as proximity to a road and a variety in ventilation strategies for homes in different locations such as in a high rise building.
This will be corrected in the next reissue of the technical manual.
