Cooking, particularly frying, is an important source of particles indoors. Few studies have measured a full range of particle sizes, including ultrafine particles, produced during cooking. In this study, semicontinuous instruments with fine size discriminating ability were used to calculate particle counts in 124 size bins from 0.01 to 2.5 microm. Data were collected at 5 min intervals for 18 months in an occupied house. Tracer gas measurements were made every 10 min in each of 10 rooms of the house to establish air change rates. Cooking episodes (N = 44) were selected meeting certain criteria (high concentrations, no concurrent indoor sources, long smooth decay curves), and the number and volume of particles produced were determined for each size category. For each episode, the particle decay rate was determined and used to determine the source strength for each size category. The selected cooking episodes (mostly frying) were capable of producing about 10(14) particles over the length of the cooking period (about 15 min), more than 90% of them in the ultrafine (< 0.1 microm) range, with an estimated whole-house volume concentration of 50 (microm/cm)3. More than 60% of this volume occurred in the 0.1-0.3 microm range. Frying produced peak numbers of particles at about 0.06 microm, with a secondary peak at 0.01 microm. The peak volume occurred at a diameter of about 0.16 microm. Since the cooking episodes selected were biased toward higher concentrations, the particle concentrations measured during about 600 h of morning and evening cooking over a full year were compared to concentrations measured during noncooking periods at the same times. Cooking was capable of producing more than 10 times the ultrafine particle number observed during noncooking periods. Levels of PM2.5 were increased during cooking by a factor of 3. Breakfast cooking (mainly heating water for coffee and using an electric toaster) produced concentrations about half those produced from more complex dinnertime cooking. Although the number and volume concentrations observed depend on air change rates, house volume, and deposition rates due to fans and filters, the source strengths calculated here are independent of these variables and may be used to estimate number and volume concentrations in other types of homes with widely varying volumes, ventilation rates, and heating and air-conditioning practices.

A year -long investigation of air change rates in an occupied house was undertaken to establish the effects of temperature, wind velocity, use of exhaust fans, and window -opening behavior. Air change rates were calculated by periodically injecting a tracer gas ( SF 6 ) into the return air duct and measuring the concentration in 10 indoor locations sequentially every minute by a gas chromatograph equipped with an electron capture detector. Temperatures were also measured outdoors and in the 10 indoor locations. Relative humidity ( RH ) was measured outdoors and in five indoor locations every 5 min. Wind speed and direction in the horizontal plane were measured using a portable meteorological station mounted on the rooftop. Use of the thermostat -controlled attic fan was recorded automatically. Indoor temperatures increased from 218C in winter to 278C in summer. Indoor RH increased from 20% to 70% in the same time period. Windows were open only a few percent of the time in winter but more than half the time in summer. About 4600 hour -long average air change rates were calculated from the measured tracer gas decay rates. The mean ( SD ) rate was 0.65 ( 0.56 ) h À 1 . Tracer gas decay rates in different rooms were very similar, ranging only from 0.62 to 0.67 h À 1 , suggesting that conditions were well mixed throughout the year. The strongest influence on air change rates was opening windows, which could increase the rate to as much as 2 h À 1 for extended periods, and up to 3 h À 1 for short periods of a few hours. The use of the attic fan also increased air change rates by amounts up to 1 h À 1 . Use of the furnace fan had no effect on air change rates. Although a clear effect of indoor -outdoor temperature difference could be discerned, its magnitude was relatively small, with a very large temperature difference of 308C (548F ) accounting for an increase in the air change rate of about 0.6 h À 1 . Wind speed and direction were found to have very little influence on air change rates at this house.

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The control of outdoor air intake rates in mechanically ventilated buildings based on indoor carbon dioxide (CO 2 ) levels, often referred to as CO 2 demand controlled ventilation (DCV), has the potential for reducing the energy consumption associated with building ventilation in some commercial and institutional buildings. Carbon dioxide DCV has been discussed, promoted, studied and demonstrated for about twenty years, but questions still remain regarding the actual energy savings potential as a function of climate, ventilation system features, and building occupancy. In addition, questions exist as to the indoor air quality (IAQ) impacts of the approach and the best way to implement CO 2 DCV in general and in a given building. This report presents a state-of-the-art review of CO 2 DCV technology and application including discussion of the concept and its application, and a literature review. In addition the regulatory and standard requirements impacting CO 2 DCV are also examined.