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INDOOR AIR QUALITY ISSUES

In a recent article dealing with a water borne musty odour, we made the point that environmental audits and assessments do not just produce dry reports but that sometimes interesting investigations result. Indoor air quality investigations, the subject of this article, are a case in point.

Early in 1995, Walters Consulting Corporation investigated a situation where an employee developed strong allergic reaction to what turned out to be her new desktop. This was compounded by an extremely low humidity situation which was quickly detected when carbon dioxide, temperature, humidity readings were taken. The workspace had been designed to have upwards of 10 air changes per hour (ACH) in order to remove the heat from modern office equipment including computer workstations.

The person knew she was unable to wear perfume and certain kinds of jewellery. An extensive analysis of the Material Safety Data Sheets for the rug, underlay, desktop, acoustic padding, wall paint, and ceiling tiles was carried out. Eventually, by using a U.S. EPA test method, TO14, it was determined that the adhesive used to bond the desktop laminate to the particle board was rosin-based. Rosin and some perfumes, in turn, are both members of the terpene family. On the recommendation of Walters, the desktop was replaced with one bonded by thermoplastic adhesive.

In order to utilize the TO14 method, an evacuated canister is used in order to collect a large sample. This sample is concentrated in a liquid nitrogen cold trap and then fed through a gas chromatograph having a high energy source as a detector. Under the influence of a high electron density beam, the molecules in the sample are broken into ions which, in turn, produce characteristic peaks in the detector. A computer compares the detected peaks to those in a library of 40,000 ion peaks and identifies the original molecule. Sometimes, two or three combinations are possible and the chemist uses skill and experience to identify the most probably chemical species.

Late in 1995, Walters was asked to investigate the indoor air quality problem of a large apartment / town house complex. Using the NIOSU 6011 method, a major odour source was found out to be chlorine. Since the unit was not close to the swimming pool area, an extensive investigation was carried out. It was determined that the discharge of the pool / sauna area was located in a stairwell adjacent to the fresh air intake. The volume of air being drawn in by the fresh air supply represented 36 ACH, so unless the wind was very strong and from the right direction, the odour laden air was readily short circuited into the fresh air intake. Walters was able to recommend a rearrangement of the ducting, which was carried out, eliminating the chlorine problem.

However, a musty odour did persist and after another investigation, it was determined that the odour originated from a particular stretch of ducting which was investigated with a video camera to locate the offending area. Musty odours of this nature are often produced by molds or fungus growing in a neglected and possibly damp corner of the duct system. In this case, Walters Consulting Corporation prepared the documentation to support a claim under the Ontario New Home Warranty Program (ONWAP).

 
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Walters Forensic Engineering | 277 Wellington Street West, Suite 800 | Toronto, ON M5V 3H2
Information contact: engineering@waltersforensic.com