The study compares on 30 ventilation systems an hygienic factor determined from conditions at air intake (including moisture before and after drainage, porosity and contamination) and microbiological analysis of air. The aim is to identify ventilation systems potential risk for indoor air contamination.The study has shown a clear relationship between the microbiologic and the hygienic conditions; i.e. dry and clean intakes are less likely to be microbially contaminated. The method seems to identify potential problems, which could be confirmed by a microbiological study.
This study presents a literature review on oil residues on HVAC components. A sampling of oil residues by filter contact method and analysis by infrared spectroscopy method have been developped. Amounts of oil residues on surfaces of components varied a lot (<10 mg/m to 700 mg/m) but were significantly correlated to odour intensity. Cleaning of oil residues from the duct surfaces with typical cleaning methods is very difficult and it is better to deliver from the manufacturer components free of oil residues.
The study monitored two similar ventilation systems with fine filters during a few months, one operating continuously, one only during day time. Air, surface and filter material samples were taken to evaluate the extent of microbial contamination with viable fungi and bacteria. Filter and air of the permanent system,with higher relative humidity, were less contaminated by microbes and the contamination was more evenly spread in the filter.
A two-years old filter was placed in a ventilation system recirculating the air in an experimental space. Via glass tubes air was extracted to an adjacent room to allow a panel to evaluate the sensory load after facial exposure, without entering the space. The sensory pollution load of the filter determined from full exposure was approximately 7 times lower than when determined after facial exposure. Even though, used filters may still be important sources of indoor air pollution.
In an environmental lab with a panel of 30 women exposed 4 hours, comfort and health have been detremined both with a used or a new filter present in the ventilation system. All other environmental parameters were kept constant. A used filter in a HVAC system can have a negative effect on both the immediate perception of the indoor air quality and on perceptions and health-related symptoms. However, the annoyance experienced through the sensory system may have amplified the intensity of symptoms.
Two aluminium windows were tested to determine the fractional penetration of airborne particles. Results show that mainly particles of 0.2 to 3 microns enter through both windows.
Two models were applied to predict particle deposition in ducts, one theoretical, the other based on experiments. These models are described and a comparison of their predictions is compared to experimental results.
The study has monitored two office buildings during 3 years changing position of dampers in order to control the air change in the buildings on periods of 3 months. CO2 levels, absenteism rate and rhinovirus in air samples are commented.
Visual inspection is a subjective method but yet necessary to control duct cleanliness. In order to improve its reliability, a visual scale has been realised and results from a panel of 10 inspectors have been compared to measurements.
Login