globally , approximately 
 40% of households rely on solid fuels  including wood , dung , grass , 
 coal , and crop residues  for cooking . the 2010 comparative risk assessment of the global burden of disease 
 attributed 3.6 million deaths yearly to the harmful byproducts of 
 solid fuel combustion for cooking and an additional 0.3 million deaths 
 from contributions of household air pollution to ambient air quality . while the proportion of households using solid fuels appears to 
 be declining , most efforts to mitigate 
 this health burden have focused on providing 
 biomass - burning stoves that vent pollution outdoors and/or improve 
 combustion efficiency to reduce emission rates . increasingly , some 
 are focused on providing access to clean energy for cooking  including 
 electricity or liquefied petroleum gas . several conditions must be 
 met if household energy interventions are to improve health : continuous 
 access to a low - emissions energy source for cooking , sustained usage of this energy source , and discarding of 
 the more polluting traditional stoves . stacking is well - documented 
 through surveys , though little objective continuous monitoring of usage of multiple 
 cooking appliances during intervention studies has occurred to date . in palwal district , haryana , we provided a fan - assisted , advanced 
 cookstove , with modifications to improve combustion efficiency ( not 
 just improve fuel efficiency or vent pollutants outdoors ) , to pregnant 
 women via local antenatal healthcare system workers . preliminary research 
 evaluating potential interventions and describing this community has 
 been published . during this initial work the philips 
 hd4012as suitable , despite requiring access to power for battery 
 charging and the need to chop the biomass fuel into small pieces . 
 among other goals , this study evaluated the use of the intervention 
 and primary traditional stoves over time and investigated predictors 
 of usage . monitoring usage and adoption of intervention stoves 
 traditionally 
 relied on simple metrics obtained through interviews or by a trained 
 observer . due 
 either to recall bias or to the influence of an outsider in the home 
 ( the  hawthorne effect  ) . recent work in rwanda , for 
 example , highlighted that usage estimates obtained from surveys were 
 biased upward relative to objective measures from electronic sensors . these biases have been well described in water and sanitation studies , 
 including recent evidence showing significant effects of structured 
 observation on behavior and attempts 
 to address these issues using simple data - logging sensors . previous studies of household energy identified 
 maxim ic s ibutton technology as an objective , field - validated 
 stove use monitor ( sum ) . ibuttons are small , coin - shaped thermometers 
 that log time - resolved instantaneous temperatures at the surface upon 
 which they are mounted . properly placed , ibuttons offer both an objective 
 measure of stove usage and a relatively unobtrusive way to monitor 
 interventions over time . this paper describes time - trends in 
 usage of the intervention and 
 primary traditional stoves in rural indian homes . we examine how well 
 short - term measures ( 1 , 2 , and 7 day mean measurements ) of stove use 
 predict study means , with the goal of optimizing sampling times and 
 strategies for monitoring household energy interventions . we believe 
 the data set described in this paper is the longest and deepest data 
 set of measured stove usage generated to date , spanning over 15 months 
 of monitoring at 10 min intervals on both intervention and primary 
 traditional stoves in 200 homes ( 21 million data points ) . 
 measuring multiple stoves required creation of new metrics to characterize 
 shifts in usage patterns over time . our secondary focus  on 
 reducing total monitoring duration for assessing use , without compromising 
 data quality  informs strategies to optimize the conflicting 
 goals of precise measurements and efficient fieldwork . this study took place approximately 80 km 
 south of new delhi at the international clinical epidemiology network 
 ( inclen ) somaarth demographic , development , and environmental surveillance 
 site in palwal district , haryana , india 
 beginning in november of 2011 and ending in march of 2013 . at the 
 time of the study , inclen was carrying out demographic and environmental 
 surveillance in 51 villages , covering a population of approximately 
 200  000 . during the study , ambient temperatures varied 
 widely by season , reaching a maximum of 45 c in may and a minimum 
 of 4 c in january ( supporting information , si , figure s1 ) . temperature data were logged every minute by the 
 project meteorological station ( onset microstation , onset computer 
 corporation ) at the inclen field headquarters in palwal town , between 
 5 and 12 km from study villages . a metal sheet stamped with a unique identifier 
 and machined with a hole was used to securely hold each stove use 
 monitor . the 
 current study focused on 7 rural villages , 
 selected based on their use of biomass for cooking , total population , 
 and their accessibility to the somaarth field headquarters . all households recruited 
 into the study used dung , wood , and crop residues in a traditional 
 hearth ( figure 1a ) as the primary means of 
 cooking . nearly all homes ( n = 200 ) cooked outdoors . the philips hd4012 ( figure 1b ) is a top - loading , fan - assisted semigasifier stove fueled 
 by small wood pieces 5 cm in length and up to 2.5 cm in diameter . it contains a rechargeable battery that powers a fan used to enhance 
 combustion efficiency . initial selection of the philips stove was based on its 
 performance in laboratory testing by the u.s . epa , which found it 
 to be among the cleanest stoves evaluated using standard simulated 
 cooking methods . field emissions from 
 this stove were evaluated by other research projects in india and our research team validated this stove s acceptability 
 in the community prior to this project . at the time of the study , the stove was produced in ghaziabad , india , 
 and sold for approximately 60 usd . participants who received 
 the philips stove were trained on proper stove use and maintenance 
 by community health workers and inclen field staff . contact information 
 for inclen s field office , which was equipped with spare parts 
 and had access to trained technicians and electricians , was provided 
 to participants in case of any stove malfunction , error , or other 
 user complaint . complaints could be filed during regular household 
 visits by inclen field staff , through calls to inclen , or by visiting 
 the field headquarters . upon receipt of a complaint , repair attempts 
 were undertaken first by inclen support staff and then , if necessary , 
 by electricians . a supply of replacement stoves was available to avoid 
 prolonged interruption in homes with stove failures . detailed logs 
 of stove reliability , malfunction , and maintenance were maintained 
 by inclen field staff ( see the si ) . upon enrollment into the study , field staff obtained informed consent , administered a baseline questionnaire , 
 and installed a sum on the primary traditional stove in each participant s 
 household . sums were placed in a custom - made metal holder and plastered onto 
 the traditional stove side wall with the same slurry of mud and water 
 used to construct and repair stoves . the holder and a sum can be seen 
 in the inset image in figure 1a . the selected 
 sums placement location did not disturb standard cooking practices , 
 was protected from overflow and spills , and captured variability in 
 temperatures adequately . stoves varied in shape and size between households ; 
 sums were placed in approximately the same location on each stove 
 throughout the study . within 4 weeks after preintervention monitoring 
 began , the philips intervention stove , prefitted with a sum ( visible 
 in figure 1b ) , was delivered to the home . a 
 custom - made metal bracket , stamped with a unique stove i d , was used 
 to hold the sums in an identical location on all intervention stoves . field workers visited homes every 2 weeks to 
 inspect stoves and download data from the sums . touch 
 and hold probe  connected to a usb to 1-wire rj11 adaptor ( maxim 
 integrated , san jose , ca , u.s.a . ) . data transfer took approximately 
 25 min per stove and involved holding the probe to the surface 
 of the ibutton . stove usage files were transferred to the field office , 
 where they were inspected for errors and minimally processed . filenames contained metadata , including stove 
 type ( philips or traditional ) , household i d , and download date . raw 
 files were archived at the field site and at inclen headquarters in 
 new delhi . cleaned files were transferred to a secure server in the 
 school of public health at the university of california , berkeley , 
 and analyzed using r 3.0 . approximately 20.6 million sums data points 
 were collected during the main study , representing 143  000 
 stove - days of data from 408 stoves . the number and duration of usage events , 
 derived from raw sums temperature traces , were determined for each 
 stove on each monitored day . algorithms for processing sums data were 
 created using an iterative process , beginning with recommendations 
 from the literature that identify events by setting thresholds for 
 the rate of increase and decrease in temperature . due to the high variability in ambient temperatures in 
 palwal , we took advantage of our continuous ambient 
 temperature measurement to adjust for diurnal variation . to compensate 
 for variability in temperatures between households and the field office , 
 we calculated the mean and standard deviation of ambient temperature 
 by each recorded hour during the study . these values were used to 
 create thresholds for evaluating whether a stove was in use or not . for each stove , the daily recorded sums temperature range ( drange ) sums data 
 were then merged with data for mean hourly ambient temperatures ( hmean  amb ) and their standard deviations 
 ( hsd  amb ) . a stove was considered 
 in use when the sums temperature exceeded the mean ambient temperature 
 plus 6 times its standard deviation . any period detected for which 
 the drange was less than 20 c was 
 marked as a period of nonuse . to count the total number of daily uses , 
 periods of use that occurred less than 40 min apart this clustering threshold was based on manual observation 
 of temperature traces . for each stove , summarized 
 data were analyzed to understand trends in usage of both the traditional 
 and intervention stoves . all analyses were restricted to households 
 for which we had at least 2 days of preintervention data ( n = 177 ) . analyses were performed separately ( 1 ) for the 
 entire data set for these households and ( 2 ) for days on which data 
 were successfully collected from both traditional and intervention 
 stoves ( see the si ) . the proportion 
 of stove use - time spent using the philips intervention stove was defined 
 as follows:1where  prop  
 is proportion and 
  dur  is duration . all durations were calculated 
 in minutes . while the proportion 
 of time spent using an intervention is useful to track adoption , it 
 does not take into account gains in efficiency of heat transferred 
 to the pot by the intervention stove , leading to shorter cooking times , 
 and thus , 
 we linked durations of cooking derived from the sums with cooking 
 power from laboratory studies to determine 
 the utilized cooking energy ( uce ) in megajoules ( mj):2where  st  is the stovetype . calculation of uce allowed estimation of changes in total energy 
 used before and after deployment of the intervention . laboratory cooking 
 power estimates were derived from controlled burning for water boiling 
 using uniform wood fuel and may not be representative of conditions 
 in the field , where multiple biomass fuels of varying moisture contents 
 may be used . the 
 metrics described 
 above were used to create a log of daily household usage , including 
 the number of uses , duration of use , and estimated energy used by 
 each stove . overall trends in use of the traditional stove before 
 and after introduction of the intervention were compared using t tests . we evaluated the change in daily mean traditional 
 stove use after introduction of the intervention using linear mixed 
 models to partition the between- and within - household variance components 
 and to calculate the intraclass correlation coefficient ( icc , the 
 proportion of variability explained by between subject differences ) . models took the following form:3where yij is the i duration of use in 
 household j , 0 is the overall intercept , bi is the random effect for 
 household i , and eij is the leftover error . this baseline model was run first for 
 the combined data set and then separately by period ( preintervention 
 and post intervention ) for the traditional stoves . we additionally evaluated how well 
 short measures of usage predicted the study average during stable 
 periods of usage . this analysis was restricted to the traditional 
 stove , which exhibited stable use patterns , and was performed independently 
 for the pre- and postintervention periods . we calculated means from 
 varying lengths ( 1 day , two consecutive days , two random days , 1 week , 
 and 1 day per month ) of usage data selected randomly from each household 
 and study period and compared it to the mean duration of use for the 
 entire study period . for these shorter measures , we calculated the 
 probability of a random measurement falling within a precision interval 
 ( for instance , within 20% in either direction of the period mean ) . during the preintervention 
 period , usage of the traditional stove was measured in 177 homes for , 
 on average , 34 days ( sd = 35 , range = 3103 ) . in this period , 
 households used their primary traditional stove 1.4 times ( sd = 0.8 ) 
 for an average of 209 min ( sd = 105 ) per day . after introduction of 
 the intervention , the traditional stove was monitored for , on average , 
 251 days ( sd = 97 , range = 52426 ) ; the philips stove was monitored 
 for , on average , 358 days ( sd = 54 , range = 139433 ) . during 
 the postintervention period , households exhibited a significant mean 
 decrease in the use of their primary traditional stove to 144 min 
 per day ( p < 2.2e-16 , sd = 134 ) once daily . the 
 intervention stove was used , on average , 0.6 times daily ( sd = 0.8 ) 
 for 60 min ( sd = 87 ) after its introduction . panels 
 show temperature traces for the traditional stove ( blue dashed line ) 
 and for the philips stove ( solid red line ) . figure 2 shows patterns of the transition 
 between traditional stoves and the intervention stove , as illustrated 
 by data from two study households . in both panels , the dotted blue 
 line is the sums trace from the traditional stove ; the solid red line 
 is the trace from the philips . pre- and postintervention patterns 
 of use are shown . in the upper panel (  mixed use  ) , 
 the philips is used upon introduction repeatedly over the course of 
 a week concurrently with traditional stove use . philips use declines 
 and tapers off in the final week . in the lower panel (  philips 
 use  ) , a third pattern , in which the philips was rarely or never used , was 
 observed but is not displayed . these types of patterns were typical 
 of the larger population during the first month after introduction 
 of the stove . use patterns during 
 the first through third months postintervention in homes with sums 
 data available on both stoves for at least 15 days per month are described 
 in table 1 . during the first month with the 
 philips , almost all homes used both stoves ( n = 152 ) . 6% of homes used the philips exclusively ( n = 9 ) ; 
 only one home did not use the philips . among the homes using both 
 stoves , the philips accounted for greater than 80% of cooking events 
 in 17% of homes subsequent months 
 exhibited wide variability between and within homes ( see the si ) . among the 9 homes that exclusively used 
 the philips during the first month , average use of the philips decreased 
 from 111 min daily during the first month postintervention to 78 min 
 daily across the remaining months . additionally , all households 
 exhibited multiple days during later months in which neither stove 
 was in use , suggesting that food was obtained by other means ( from 
 relatives or purchased ) , cooked in alternate locations , or cooked 
 using stoves not fitted with sums . similar trends were noted for homes 
 exclusively using the philips in months two and three . no use of either stove recorded . the variability in usage of the intervention and the 
 lack of displacement 
 of cooking tasks from the traditional stove to the intervention is 
 emphasized at the study population scale in figure 3 . between introduction of the intervention and postintervention 
 day 200 , there is a significant and consistent decrease of 0.28 min / day 
 in use of the philips ( p < 2e-16 ) ; between day 
 200 and the end of monitoring , usage stabilizes but continues to decrease 
 by 0.04 min per day . similar trends were noted for daily use event counts over 
 time ( see the si ) . most of the total variability 
 in usage across stove types was due 
 to variability within homes : 66% across periods for traditional stoves 
 and 78% for intervention stoves . the total variability was highest 
 for traditional stoves in the postintervention period , perhaps indicative 
 of either a shift first to and then from the philips or mixed use 
 of both stoves . si table s3 shows the means 
 of use duration overall and by stove type and period and presents 
 the calculated iccs , the proportion of variability explained by differences 
 between subjects . prior to 
 the intervention , 
 households utilized 15.5 mj of energy per day ( sd = 1.5 ) from cooking 
 with their traditional stoves ( figure 4 ) . after 
 introduction of the intervention stove , utilized cooking energy from 
 the monitored traditional stove decreased significantly to 10.6 mj 
 per day ( sd = 0.86 , p < 2.2  10 ) . in the first month after introducing the intervention , however , 
 total average utilized energy increased to 21 mj daily , due to use 
 of both stoves . counterintuitively , perhaps , decreasing usage of the 
 more efficient philips in subsequent weeks led to decreasing total 
 energy use . assuming the rate of energy consumption of each stove 
 remained constant throughout the study , the average daily utilized 
 energy across the postintervention period increased to 16.3 mj ( p 
 = 0.003 ) . the utilized cooking energy is presented separately for the traditional 
 and intervention stoves ( blue and red , respectively ) and pre- and 
 postintervention periods . of cooking duration1 day , 1 day per study month , 2 random 
 or 2 consecutive days , and one consecutive week  to predict 
 mean stove usage of the traditional stove during the pre- and postintervention 
 periods . these periods for the traditional stove were selected because 
 they exhibited relative stability over time , as compared to the philips . short measurements had a low probability of predicting the study - wide 
 mean of stove usage . precision varied across the pre- and postintervention 
 periods ( si figure s5 and table s4 ) . short - term 
 measures adequately predicted preintervention means with traditional 
 stoves . during this period , a consecutive week of sampling had the 
 highest probability ( 75% ) of being within 20% of the long - term mean . just 18% of random single days were within 20% of the long - term 
 mean for the traditional stove . the mean of samples taken for 1 day 
 per month postintervention had a 66% chance of being within 20% of 
 the long - term average . we report on the usage 
 of an intervention stove distributed to 
 177 pregnant woman and related changes in use of the traditional stove 
 over approximately 60 weeks in rural india . the data set consists 
 of one of the largest and longest objective measurement campaigns 
 of stove usage to date . by deploying stove use sensors for over a 
 year , we were able to track and report for the first time the changes 
 in usage of an advanced cookstove intervention and the primary traditional 
 stove over time . few algorithms 
 for converting temperature traces to event counts and durations of 
 use have been published . we offer a novel analysis method : usage events 
 defined as periods that deviate from ambient temperatures . this method 
 does not rely on any additional assumptions about the distribution 
 of the data and facilitates relatively fast analysis of large volumes 
 of data . it does , however , require local measurement of ambient temperature , 
 which can introduce additional cost . we focus on durations of use , 
 as we believe this to be a more health - relevant metric and a better 
 indicator of potential risk than number of events , which can be easily 
 obtained from duration data if needed ( see si ) . further evaluation of this algorithm is ongoing on both 
 previously collected and new sums data sets . we are additionally investigating 
 the feasibility of household or village level  ambient sums  
 to aid with signal processing and to account for microclimatic variability 
 not captured by a single , meteorological station . finally , we are 
 monitoring usage on many different stove phenotypes globally ; these 
 activities will help optimize sums placement practices , and evaluate 
 and hone the described algorithm to determine its broader applicability . we see a need for standard methodologies for interpretation of 
 ibutton signals that cater to specific research or programmatic goals . daily time of use and number of uses are simple metrics obtainable 
 from sums data through a number of methods . interstudy comparisons 
 of usage may be complicated , however , by the algorithm design decisions 
 used to generate these metrics . for instance , time - of - use is impacted 
 by the threshold at which the stove is no longer considered to be 
 on ; the number of uses is similarly affected by decisions about clustering 
 of temperature peaks . clear specification of algorithm 
 parameters  ideally in the form of open - source code  and 
 evaluation of algorithms in multiple studies can help clarify differences 
 between methods . we found continuously 
 decreasing population trends in usage of the intervention stove over 
 time . this trend leveled off between 175 and 200 days postintervention . 
 while usage of the intervention had not completely ceased at the end 
 of data collection , the number of homes using the intervention stove 
 regularly and the related durations of use were lower than immediately 
 after stove distribution . our findings are supported by other studies 
 that 
 have ( 1 ) indicated  stacking  of devices throughout 
 the adoption process and ( 2 ) acknowledged 
 a trial period during which the household evaluates the suitability 
 of the intervention . utilized cooking energy 
 showed similar trends , with an increase in total uce following introduction 
 of the philips followed by a leveling off and stabilization . future 
 studies should focus on similar calculations to understand if there 
 is a setting , addition of the advanced stove seemed to increase overall 
 energy use , perhaps because the users took advantage of an additional 
 stove to provide more cooking services rather than substituting the 
 philips for the traditional stove . any future studies seeking to calculate 
 uce should evaluate cooking power in the field , as laboratory and 
 field stove performance parameters often vary widely . because we relied on these laboratory estimates and applied them 
 uniformly over the study period , we may be mis - estimating the actual 
 utilized cooking energy . our findings indicate that the philips 
 may have temporarily offset 
 a portion of measured traditional cookstove usage , albeit in a way 
 that may have increased total energy use . despite this continued use 
 of the philips , however , it failed to become the dominant stove used 
 in the home , as would be necessary to maximize health protection . importantly , without measurement of usage of both 
 the primary traditional 
 and intervention stoves , we would have been unable to make any determinations 
 about the role of the philips  as an added cooking appliance  in 
 household cooking . finally , we would not have observed the initial 
 uptick and subsequent decrease in uce after introduction of the intervention . the high within - household variability 
 of daily usage of both stoves  especially in the postintervention 
 period  indicates that care must be taken when using short - term 
 measures of usage to predict long - term means . this stands in stark 
 contrast to previous work in guatemala , where the majority of variability was found to be between households . most likely , this is due to the difference between the character of 
 the intervention in guatemala , which was well - known to the community 
 and locally created , and the intervention in india , which while vetted 
 in the community was an engineered object brought in from elsewhere . continuous measurements allowed us to evaluate the ability of short - term 
 measurements to predict the long - term mean . short - term measurements 
 of one or two consecutive days did a poor job of predicting the long - term 
 mean , with the majority of measurements deviating from the mean by 
 over 20% . for instance , 
 one 24 h measurement per month of the study  were much closer 
 to the long - term mean . these findings suggest that future intervention 
 studies should measure stove usage regularly to capture inherent variability 
 in household behavioral patterns and to best capture changes in usage 
 over time . given that short - term measures fail to accurately predict 
 long - term means in relatively stable situations , their value in dynamic 
 situations , such as the days and weeks following intervention introduction , 
 is limited . attempts to assess adoption and use must track behaviors 
 consistently for longer periods of time . although promoted by village health workers , the stoves 
 were given to participants free - of - charge , which has been shown to 
 impact perceptions of value . participants 
 were enrolled based on pregnancy during the initial phases of the 
 study and may not represent the broader population . cultural cooking 
 practices related to pregnancy may impact adoption of an intervention 
 stove ; initial and long - term usage in households without a pregnant 
 woman may be more consistent or significantly different from the patterns 
 we observed . however , as our study population represents a particularly 
 vulnerable group , indications on how they use this free intervention 
 can inform future studies targeted toward similar communities . second , 
 we were unprepared to instrument the other traditional stove types 
 found in many households . while we placed two sensors , one on the 
 intervention stove and one on the participant - reported primary traditional 
 cookstove , it is possible that other traditional stoves were also 
 used during the study period . further , there is possibility of the 
 hawthorne effect : instrumentation of the primary traditional cookstove 
 may have shifted usage to other , unmonitored traditional stoves . among 
 users who exclusively used the philips during month 1 or 2 of the 
 study , we noted multiday periods of inactivity with both monitored 
 stoves in subsequent months , indicative of cooking elsewhere or use 
 of another stove . we believe either of these reasons may account for 
 the higher levels , on average , of traditional stove usage in the preintervention 
 period . as a result of these caveats , our study paints only a partial 
 picture of the true usage patterns in the home . as these secondary 
 and tertiary stoves were reported to be used only for simmering milk 
 or cooking during inclement weather , we do not believe there were 
 wide changes in their use as a result of introduction of the philips . we can not , however , discount the possibility of use of unobserved 
 and unmonitored stoves . the fieldworker burden for this study was high , with a 
 small team of fieldworkers visiting each household every 2 weeks . households were spread over a relatively wide area , leading to significant 
 transit time and costs and fieldworker turnover . similarly , the volume 
 of data proved to be a logistical challenge to manage , clean , and 
 transfer . strict protocols and fieldworker assurances facilitated 
 analyses but could not , inherently , decrease data transfer and processing 
 times . sums on traditional stoves were especially difficult to maintain 
 over long periods of time due to challenges with placement related 
 to overheating and exposure to water ( see si ) . we are exploring alternate measurement techniques  including 
 infrared thermometers , thermocouple - based data - loggers , and wireless 
 transmission of data  to improve data completeness and fidelity 
 for traditional stoves . comparisons of data measured with sums to 
 participant - reported stove use and perceptions of the philips as a 
 replacement for the traditional stove are in preparation . such comparisons 
 have , in some cases , revealed that reported 
 stove use is similar to measured use , while in other cases reported 
 use exceeds measured use . future intervention 
 studies should focus on long - term objective measurement of stove use 
 and seek a deeper understanding of the individual and community behaviors 
 motivating use or nonuse of an intervention through qualitative methods 
 from behavioral science . stove usage is a critical link between 
 the potential and delivered 
 benefits of intervention programs . monitoring 
 of usage over time is necessary to fully understand the potential 
 for delivery of those benefits ; in this study , short - term measurements 
 of benefits immediately after intervention distribution would have 
 been misleading and potentially led to mistaken claims of benefits . the low long - term usage of the intervention stove , while disappointing , 
 is informative . it indicates ( 1 ) that preliminary work , while valuable 
 to assess initial feasibility of an intervention , will most likely 
 not predict long - term viability ; ( 2 ) that measurement of usage of 
 both traditional and intervention stoves is required  over time to 
 fully understand and accurately characterize adoption of an intervention 
 and changes in traditional habits ; and ( 3 ) that a combination of more 
 transformative , aspirational interventions  that can fully displace 
 the traditional stove  and education and training , to sway participants 
 away from the old stove , will be required to fully realize benefits .
household 
 air pollution generated from solid fuel use for cooking 
 is one of the leading risk factors for ill - health globally . 
 deployment 
 of advanced cookstoves to reduce emissions has been a major focus 
 of intervention efforts . 
 however , household usage of these stoves 
 and resulting changes in usage of traditional polluting stoves is 
 not well characterized . in palwal district , haryana , india 
 , we carried 
 out an intervention utilizing the philips hd4012 fan - assisted stove , 
 one of the cleanest biomass stoves available . 
 we placed small , unobtrusive 
 data - logging ibutton thermometers on both the traditional and philips 
 stoves to collect continuous data on use patterns in 200 homes over 
 60 weeks . 
 intervention stove usage declined steadily over time and 
 stabilized after approximately 200 days ; use of the traditional stove 
 remained relatively constant . 
 we additionally evaluated how well short - duration 
 usage measures predicted long - term use . 
 measuring usage over time 
 of both traditional and intervention stoves provides better understanding 
 of cooking behaviors and can lead to more precise quantification of 
 potential exposure reductions and consequent health benefits attributable 
 to interventions .