Empirical and theoretical investigations of
fine particle emission from cooking
Publication Date
July 24, 2020
Creator
Abstract
Exposure to fine particulate matter with diameter < 2.5μm (PM2.5) is associated with elevated risks of acute and chronic health effects. These health effects are established for ambient PM2.5 concentrations; however, the average UK resident spends 70% of their time indoors at home. PM2.5 is also a criteria indoor air pollutant, so indoor PM2.5 concentrations could contribute more to total personal exposure. Cooking is a primary PM2.5 source in non-smoking dwellings. Crucially, with cooking, complete source removal is not feasible; instead ventilation strategies are used to dilute PM2.5 concentrations or to remove emitted PM2.5 at source. In response, this thesis used empirical and theoretical methods to measure and predict PM2.5 concentrations in dwellings of the English housing stock, and to test the suitability of the current ventilation requirements of the English building regulations to mitigate against PM2.5 emitted during cooking. This investigation was composed of three stages.
First, concentrations were measured in the kitchens of five multiple occupancy student dwellings situated in Nottingham, UK. Measured PM2.5 concentrations were elevated above background levels during cooking. A behavioural intervention to encourage ventilation use during cooking resulted in a statistically significant, small decrease in concentrations in two of the five houses. Changes in cooking activity between the measurement weeks was a confounding factor.
The second stage was to develop a method to measure emission rates, using toasting bread as a simple repeatable source. Key factors for a repeatable test were controlled mixing and ventilation conditions, sufficiently small concentration logging interval, and determining custom calibration factors using gravimetric sampling to ensure accurate mass measurements. A total of 40 tests were used to produce an empirical cumulative distribution function of emission rates from toasting bread. Emission rates from cooking full meals composed of multiple stovetop processes were measured following an adapted method. Concentration profile, average emission rate, source strength and calibration factor all varied between meals. Therefore, concurrent gravimetric sampling is imperative when using optical devices to monitor cooking source PM2.5 concentrations. Frying in a non-stick pan and using a cooker hood during cooking reduced room emissions, and so are recommended to minimise occupant exposures.
In the final stage, probabilistic modelling techniques were used to predict 24-hour average concentrations in kitchens of the English housing stock. Over 98% houses were predicted to be too airtight to sufficiently dilute concentrations by infiltration alone. Current ventilation requirements from the building regulations were predicted to be adequate in less than 11% houses, which improved to 46% when intermittent ventilation was continued for 10 minutes after cooking. Therefore, householders are recommended to use externally exhausting mechanical ventilation throughout cooking and for a further 10 minutes. Recommended ventilation rates for concentrations to remain below guidelines in 75% kitchens are 61 L/s (11 h^-1) constant or 79 L/s (13 h^-1) intermittent ventilation during cooking and for a further 10 minutes. The relationship between cooker hood airflow rate and capture efficiency was defined in the form of a design tool. A cooker hood with high capture efficiency is recommended to achieve the same air quality at lower ventilation rate, and consequently lower noise and energy impacts.
Item Type
ethesis
Thesis Type
PhD
Supervisors
Subjects (LC)
Associated Schools / Departments
Faculty of Engineering
Department of Architecture and Built Environment (UK)
eprints ID
59766
UoN Repository URI
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Catherine_O'Leary_PhD_Thesis.pdf
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Full-text
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Format
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