Estimated distributions of PM2.5 concentrations in the kitchens of the English housing stock for infiltration and mechanical ventilation scenarios

Exposures to elevated concentrations of airborne fine particulate matter with diameter ≤ 2.5 µm (PM2.5) have been linked to multiple negative health effects. Investigations into PM2.5 exposures primarily focus on external concentrations, which are easier to monitor. However, there is a growing interest in indoor exposures, as people spend up to 70% of their time at home, concentrations in dwellings may have a greater influence on personal exposures. As widespread indoor monitoring is difficult, modelling can offer an alternative method to investigate concentrations in a stock of houses. 
Cooking has been identified as a key source of PM2.5 in non-smoking households. Existing models are sensitive to the emission rate used, yet typically represent cooking sources with a constant emission rate, despite emission rates having been shown to vary with food type and cooking method amongst other factors.  
Ventilation rates are another determinant of concentrations. Whilst the English Building Regulations require purpose-provided, mechanical extract ventilation to be installed in kitchens of new dwellings, for existing dwellings, there is only a requirement to maintain existing installations. Furthermore, there is no guarantee that occupants use installed ventilation, therefore it may be useful to consider an infiltration-only scenario, as a worst-case. 
This paper investigates steady state PM2.5 concentrations in kitchens in the English housing stock using simple statistical modelling. A Monte-Carlo simulation is used to produce a distribution of steady-state concentrations under worst-case conditions, considering infiltration as the only form of ventilation. A probability density function (PDF) for PM2.5 emission rates for toast is used, a source the authors have investigated. Kitchen input data was taken from the English Housing Survey, a statistically representative sample of the English housing stock. 
For worst-case conditions, the steady-state concentration is predicted to exceed 25µg/m3 (the WHO daily mean guideline) in all kitchens. Mechanical ventilation is predicted to reduce the steady-state concentrations for all scenarios considered. A capture efficiency > 60% for a cooker hood extracting at 30l/s has equivalent performance to a general extractor fan with an airflow rate of 60l/s. However, in the best case scenario considered, steady-state concentrations are predicted to exceed the WHO daily guideline in 30% of kitchens. This is for air extracted at 30l/s through a cooker hood with 80% capture efficiency.