Indoor Air Quality Case Study

Pinchin Environmental was retained in early 1998 by a community services organization for assistance with chronic indoor air quality complaints in their Mississauga, Ontario office. Staff had complained for several years of odours leading to a range of health complaints in this leased facility. Despite inspections and some interventions from the landlord, gas utility, municipal Public Health office, and the Ministry of Labour, complaints continued. These were serious enough that several staff had missed part-days or entire days due to headache and nausea. The organization had explored every option they could identify, and were considering leaving the building prior to the end of their lease.

The office area is approximately 600 square metres. Occupancy varies during the day due to the nature of the work, and at times over 30 staff are present in the building. This leased space is part of a strip plaza containing a range of light industrial and commercial facilities. The neighbouring tenants were, to the west, an automotive service centre, and to the east, a graphics firm. The graphics firm was a recent tenant, and replaced a home brew outlet previously in that space.

Further to the west were a welding school and a few warehousing operations. The organization had experienced some difficulties with the automotive centre next door, especially when the odour of automotive exhaust coming from vehicles idling outside their front door was drawn into the rooftop air handling unit.

Log of odours and complaints

The indoor air quality investigation was helped considerably by a log of odours and complaints that the organization had kept since 1996. This log also recorded the service calls on the two rooftop package heating and air conditioning units. Health complaints during this time included headache, nausea, burning and dry eyes, and fatigue. Several complainants reported that symptoms and odours were strongest first thing in the morning. The log recorded several episodes of strong odours, including a chlorine odour, brewery smells (which staff associated with the neighbouring home brew store), and several references to "gas" odours and the smell of burnt oil. The reports of gas odour prompted an immediate inspection by the natural gas utility, which found all piping, including the rooftop units, to be in good order.

The staff in this office had strongly suspected that some of their complaints were due to the neighbouring automotive service centre. In the past, clients of the centre and mechanics in the centre had left vehicles idling immediately in front of the centre, and at times when the wind was light and from the south, the exhaust odours would enter the office through the front door.

There had also been a few episodes when the exhaust of diesel-powered delivery trucks parked at the rear of the plaza had been drawn into the office, either through the rear doors, or through one of the rooftop units.

Action taken to reduce odours

The landlord and our client had completed a few actions to help reduce the odours in the office. The neighbouring automotive centre had been asked to stop the practice of leaving idling vehicles outside the office door, and to keep delivery trucks from idling at the rear of the plaza. The landlord had also arranged to have the supply air dampers on the two rooftop units closed off, to prevent infiltration of odours. To make up for the lack of fresh air, a 300 cfm fresh air supply fan was located at the extreme rear of the unit.

The air intake for this unit was from a stack of about 3 metres in height, and the unit was located as far upwind in relation to the prevailing winds as possible, to minimize odour infiltration from the front of the building. The fresh air unit was probably providing sufficient outdoor air, as carbon dioxide concentrations measured through the offices in periods of peak occupancy were a maximum of 900 ppm.

As the automotive service centre was presumed to be the source of most of the odour complaints in the office, a careful inspection was made above the ceilings of the offices, to look for penetrations through the common wall that could be a route for the odour to enter the office space through the ceiling return air plenum. No penetrations were found, and the seal of the demising wall at the roof line appeared tight. However, an inspection on the roof revealed a much more likely source of odours, which had not been identified in any of the previous investigations. Located about 20 metres immediately upwind of one of the rooftop units serving our client's space was the exhaust of the tailpipe exhaust unit from the automotive service centre. The emissions from this unit would include 100's of ppm of carbon monoxide, and a strong odour of gasoline and diesel exhaust. Furthermore, the exhaust unit, rather than being discharged upward to help in dispersion, was horizontally discharged along the roofline, directly towards one of the rooftop units serving this office. Although the air intake dampers on the downwind unit had been set to the closed position, such dampers generally leak a minimum of 10%, so that there was good chance that the automobile exhaust odours unit would be occasionally or frequently drawn into the rooftop air supply unit. The timing of the complaints, which according to the IAQ log occurred more frequently in the morning, is consistent with the usual sequence of operations in a garage, where the vehicles are typically run first thing in the morning to diagnose problems, and not usually run as much for the remainder of the day.

Likely source of odours identified

Having identified the automotive centre exhaust as the likely source of most of the odours, we recommended that the exhaust unit be vented vertically, and at a height to minimize impingement of odours at our client's rooftop unit. Also, the air intakes to the rooftop unit were to be sealed airtight with sheet metal and caulking, rather than relying on the dampers being closed. These repairs were completed in the summer of 1998. Since that time, the intensity and frequency of odour complaints has lessened, although not completely.

The lessons to be drawn from this IAQ investigation?

• Never overlook the obvious, and certainly inspect all equipment on the rooftop.
  
  
• Be careful of terminology in the complaints given by occupants. On report of frequent "gas" odours, the gas utility was called in to inspect. However, when the complainants were interviewed regarding the odour they had experienced, on prompting they most commonly identified the odour as gasoline-like.
  
  
• Although provincial environmental law made the automotive service centre responsible to ensure that their emissions would not create a nuisance or health hazard at the neighbour's property (in this case it would have been deemed to be the intake of the rooftop HVAC unit), our client found it very difficult to get either the landlord or the provincial environmental authority to enforce this requirement. Certainly, the landlord found the frequent complaints difficult to manage. Landlords of mixed-use developments should be mindful to keep operations with any rooftop emissions from being anywhere near more sensitive tenants.

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