exposure

Cooking can be a major source of exposure to particulate matter. Range hoods can be used to reduce odours, moisture and contaminants resulting from cooking. The capture efficiency with regard to these contaminants is determined by the thermal plume and the aerodynamic properties of the range hood. There is a new ASTM (an international standards organization) test method: ASTM E3087. It measures capture efficiency under specific conditions that permits standardized comparison of range hoods under controlled laboratory conditions.

A systematic and efficient strategy is needed to assess and manage the potential risks to human health that arise from the manufacture and use of thousands of chemicals.  For both volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs), exposure is strongly influenced by the types of materials and products in which the VOC or SVOC occur, the concentration of the VOC or SVOC in the material or product, the way in which the material or product is used or applied indoors, and the ventilation rate within the room or building.

The role of ventilation in achieving acceptable indoor air quality is examined in the light of emerging challenges, alternative mitigation strategies and performance indices within the spatial and time matrix of the indoor environment. By considering the source of contaminants, their nature, transportation mechanism and participation in source-sink relationships, several studies have shown that it may not be feasible nor adequate to rely on ventilation alone to attain the desired level of exposure, especially with respect to airborne aerosolised droplets with infectious potential.

This study developed a drift-flux model for particle movements in turbulent indoor airflows. To account for the process of particle deposition at solid boundaries in the numerical model, a semi-empirical deposition model was adopted in which the sizedependent deposition characteristics were well resolved. After validation against the experimental data, the drift-flux model was used to investigate human exposures to particles in three normally-used ventilation types: mixing ventilation (MV), displacement ventilation (DV), and under-floor air distribution (UFAD).

About two hundred volume traps were retrieved from dwellings in various radon prone areas inEurope. They were analysed for the purpose of retrospective radon assessment. Emphasis is put onspecific problems encountered when using field samples as opposed to laboratory exposed samples. Itwas seen that in very dusty circumstances, direct penetration of radon decay products from the outsideto the centre of the volume traps calls for extra caution. Rinsing the samples is proposed as a solutionand was tested in field and laboratory conditions, showing good results.

This study investigated the feasibility of using the spatial distribution of expiratory aerosols and thepercentage viability of airborne viruses to estimate the spatial exposure levels of airborne viruses inrooms under imperfectly mixed condition. Experiments were conducted in a hospital ward withceiling-mixing type ventilation system. A broth solution with a known concentration of bacteriophages,as to simulate airborne viruses, was aerosolized with a droplet size distribution similar to humanexpiratories. Spatial distributions of these aerosols were measured using an aerosol spectrometer.

A new mechanical ventilation system which continuously controlled the indoor-outdoor pressure difference was installed in six houses, where the long-term radon levels ranged from 670 to 3 080 Bq/m³. When the new system had operated for several months, the indoor radon levels decreased to levels from 120 to 600 Bq/m³ , the effective dose reductions being from 40 % to 88 %.