the effects of electrostatic particle filtration and supply-air filter condition in classrooms on the performance of schoolwork by children (rp-1257).

Many studies report high concentrations of particles in the classroom (EFA 2001; Dijken et al. 2005; Simoni et al. 2006)
But until recently, no one has shown that removing particles from the classroom can improve school performance.
The only study directly examining this hypothesis is a recent field experiment in Sweden to operate or disable electrostatic air purifiers in two pairs of classrooms (
Mattsson and Hygge 2005).
This study focuses on the possible benefits of air purifiers for children with allergies or allergies and is therefore conducted during the pollen season.
The air purifier reduces the concentration of particles in the air and tends to reduce the number of cat pollen, although this effect is not statistically significant (Mattsson et al. 2004).
When the air purifier was running, the children \"claimed to be sensitive to particulate matter contaminants in the air\", and eye and airway stimuli were significantly reduced, and these students scored 25% higher on one of the five performance tests (
Find synonyms);
However, multiple tests (i. e. chance)
Could be a possible reason for this isolated result.
It has always been believed that inhaled particles in indoor air must have some negative effects on health, which may have a negative impact on mission performance.
The origin of this hypothesis is that in the absence of additional indoor sources such as burning, cooking or smoking, indoor particles are largely the same particles found outdoors (ambient)air (Fromme et al. 2005)
Based on reliable epidemiology evidence, they do have a negative impact on the health of older people with pre-syndrome
There are medical problems in asthma patients of all ages (NRC 2004; Dominici et al. 2006; Hartog et al. 2003; Peters et al. 1997)
For children (
Ward Andres 2004;
Moshammer, etc. 2006).
Despite this evidence, a major literature review of 1725 recent publications on the health effects of particles in indoor air (EUROPART)
It is concluded that \"there is insufficient scientific evidence that indoor specific substances or quantitative concentrations in the air can be used as a universally applicable risk indicator for health effects in non-industrial buildings \"(Schneideret al. 2003).
The concentration of indoor particles can be reduced by installing electrostatic deposition air purifiers and particle collection devices to remove particles from flowing gases (such as air)
Use the force of the inductive static charge.
The electrostatic air purifier can remove tiny air particles very effectively (Mattsson et al. 2004; Croxford et al. 2000; Skulberg et al. 2005)
Including abnormal reaction particles (
Hackers and sparrows 2005Francis et al. 2003;
Van der head and others. 1999)
, Their concentration in the school classroom is usually as high as the home of the pet owner (Almqvist et el. 1999; Bergeet al. 1998).
However, the operation of the electrostatic air purifier does not bring benefits to the occupants.
Free installation-
In London\'s office, vertical electrostatic air purifiers with disposable deposition plates reduce the concentration of small particles [
Less than or equal to]2[micro]m (PM2)
More scores than they restore larger scores (PM10)
But no surface dust is reduced (Croxford et al. 2000)
No effect on symptoms reported by office occupants (Wyon et al. 2000).
In a similar intervention experiment in the Norwegian office, the operation of the electrostatic air purifier reduced the dust concentration, but had no significant effect on the reported symptoms (Skulberg et al. 2005).
Rosen and Richardson (1999)
Ion generator operating (
No deposit plate)in two day-
Three nursing centers in Sweden
A year\'s study reported that their intervention reduced the number of small particles by 78% and the number of largerparticles by 45%, but in both institutions only one was absent due to illness
Over time, absenteeism under control conditions has changed significantly, suggesting that this obvious effect of the intervention may be due to external factors.
This experiment was designed to determine whether reducing the concentration of particles in the air of the school classroom would improve the performance of school children\'s homework and whether the conditions of bag dust collectors in the ventilation system would affect this.
These experiments are part of a larger study that investigates the impact of improving classroom conditions on academic performance (
2007a, 2007a).
Methods experimental design this study is a series of field experiments in the classroom where children normally complete their studies.
These are cross-experiments in a pair of classrooms that operate or disable electrostatic air purifiers during the same week in adjacent classrooms.
In the second week, the operating mode of the electrostatic air purifier switches between classrooms (
Cross design)(see Table 1).
The main advantage of this design is that in a given week, any external factors that affect performance, environmental perception, and symptoms also affect the results obtained under the two conditions determined by that week,
In order to eliminate any random deviations resulting from symptom intensity or individual differences in completion of academic ability, the experiment was conducted in a repetitive manner
Measurement design.
The experiment 1EF conducted in January 2005 is a 2x2 design in which each operating mode of the air purifier is re-implemented after replacing the old and new supply
Air particle filter.
Experiment 2EF was conducted on 2005-
Air filters have been in use for months.
Both experiments were conducted outside the pollen season to avoid this additional source of sensitivity differences.
During the experiment, teachers and students are allowed to open and close doors and windows according to their usual habits.
The schedule of normal school activities has not changed in order to maintain the teaching environment and routine as much as possible.
The interventions were approved by parents, teachers, school boards, local authorities in charge and the ethics review board.
The consent of the child was not sought so that they would not turn a blind eye to the experimental conditions.
Schools, classrooms and ventilation experiments are conducted in five public primary schools, which are opened by local authorities for children under the age of 616 years (see Table2).
The school building is made of bricks with floor covering and typical school furniture in the classroom;
Outdoor clothing used by students is left outside the classroom and smoking is not allowed.
All classrooms are ventilated using a mechanical ventilation system that provides 100% outdoor air filtration and preheating in Central Airhandlingunits (AHUs)
With or without heat recovery;
Cooling or humidifying is not provided (see Table 2).
AHUs is operated intermittently (
System in 9-
Rest 10 hours a day on weekends and school holidays).
In a given experiment, each pair of classrooms has an outdoor air supply from the same AHU.
About 190 studentsto-twelve-year-
The old children participated in the experiment;
The children were generally healthy but did not undergo prior medical examination and did not receive information about how many children had allergies in the study.
Static air purifier (
Design according to the principles described in detail by Torok and Loreth [1993])
Inca beer is installed on the walls of each classroom.
They can hardly hear. -
The noise level generated by the fan is about 30-35 dB(A).
Contrary to other electric vacuum cleaners reported in the literature (Niu et al. 2001)
They do not produce ozone;
Prior to the installation of the air purifier in the classroom, laboratory tests conducted by the experimenter confirmed this.
In experiment 1EF, two air purifiers are installed in each classroom, and three air purifiers are operated in each classroom in experiment 2EF.
The airflow of each cleaner is 800 [m. sup. 3]/h (470. 9 cfm); i. e.
The total airflow of the air purifier is equivalent to 8-12 ach.
According to the manufacturer\'s specifications, the efficiency of the air purifier is 99%, So Clean
The air delivery rate is similar to the flow through the unit.
No reduction in particle concentration under reference conditions: installed and operated cabinets with fans but without deposition plates or ion generators in experiment 1EF, at experiment 2EF, the unmodified electrostatic air purifier continues to work and the corona effect is disabled.
Therefore, the fan that installs the cabinet always runs in position.
In experiment 2EF, six identical air purifiers were used in rural schools and six other identical units were used in urban schools.
The same deposition panels were used during the experiment.
In experiment 1EF, power supply-air filters (
EU7 class bag filter)
At the beginning of each experiment, either new or used;
They are the same filters used in another experiment, parallel to experiment 1EF in the other two classrooms of the same AHU service (
Wayne Wargockiand 2007a).
The filter has been in use for 12 months.
After the children leave the classroom, use the adust monitor at the end of each week for physical measurement of air particle density for 20 minutes on-site measurement;
Size range for evaluation> 0. 75, >1,>2, >3. 5, >5, >7.
5,> 10 and> 15 [mu]m.
Super Particle counter with size range of 0. 02-1 [mu]M is also used. PM2.
5 and PM 10 were not measured because the purpose was to check whether there was an impact on particle concentrations of different sizes, rather than comparing the measured concentrations to the requirements in the standard.
No allergens were measured.
Trace dust deposits to the horizontal plane to measure byplacement clean glass plates every week (child-proof)height of 2. 2 m(7. 2 ft). A surface-
Over the weekend, the dust meter was used to evaluate the percentage of the surface covered by the dust.
This is achieved by using forensic gelatin tape to lift the dust and then inserting the velvet sheet into an instrument that measures the amount of light scattered by the alaser beam.
Temperature, relative humidity (RH)
, Carbon dioxide is continuously measured and field measurements of the airflow speed, noise and operating temperature of the classroom are supplemented in experiment 1EF.
Continuous measurements are used to calculate the weekly average of children in the classroom, excluding short breaks during teaching.
[Requirements]CO. sub. 2]
As with previous experiments, when students appear in the classroom, it is used to estimate the effective ventilation rate (
Wargocki and WHYN 2007a, 2007a).
The instrument has been calibrated before use.
Weather data were registered throughout the period.
Weekly performance measurement, in the appropriate course, the children\'s teachers manage the language of the parallel version
From reading to mathematics, basic and mathematical performance tasks represent different aspects of the curriculum.
Lack of cooperation due to teachers in Classroom 2-1 of the school
In experiment 2EF, the experimenter showed the task in the presence of the teacher.
The presentation of tasks throughout the week is fairly uniform, and teachers are required to always apply the same tasks on the same working day.
No more than one task is performed in a class, and usually no more than two tasks are performed every day.
These tasks were selected as the natural part of the general school day, including multiplication, subtraction, digital comparison, logical thinking, reading and understanding, and proof of acoustics
Read, as described in detail by byWargocki and Wyon (2007a, 2007b).
Digital comparison and sound insulation-
Experiment 2EF omitted the reading task.
The teacher teaches the children how to complete the task by working with examples of classes to ensure that the children understand each task.
In the case of the experimenter presenting the task, the instruction is played from a pre-recorded CD in the child\'s own language.
The duration of the task is short enough to ensure that most children are unable to complete the task within the time available.
Assign up to ten minutes per task.
If any student has completed the task before the allotted time, the teacher will immediately tell all other students to stop and record the actual time that has passed.
Each task is prepared with a different version, and the task version is confused on different occasions. e.
, Always encounter version 1 before version 2, and so on.
The task is presented to the children in their own language (
Danish or Swedish).
Performance in terms of speed (
How fast each student is working in unit time)and errors (
Percentage of mistakes made).
In the case of sound insulation
When reading, only errors and false positives are recorded, because the speed of performance is determined by the speed of text dictation.
A complete design analysis is first used to analyze children\'s performance. e.
, Only analyze the results of the students who participated in the test under all conditions, and then repeat the analysis using all available data, I . E. e.
, Including the performance of students who do not exercise under all conditions (
Incomplete design).
If there is a big difference in performance on different occasions-
Ignoring interventions, perhaps due to learning, increases familiarity with differences between exercise, fatigue, or beta versions ---
After adjusting the results of this effect, the analysis was repeated.
The adjustment is by multiplying the individual performance of each student on a given task by the coefficient (C)
Calculated as C = A/B, the ratio of the average grade of the student class in the first week of the introduction task (A)
The average performance of the student class on that week\'s task (B).
Then, the performance of each individual task is standardized by dividing the average performance of the task in each experiment without considering the conditions.
Perception of visual markers in children and measurement of symptomsanalogue (VA)
In the last class every Friday, a scale test is conducted once a week to indicate the intensity of various symptoms and their perception of the environment (Figure 1).
The project VA scale includes the following contents: Perception of classroom temperature; air movement; air dryness; air freshness;
Illumination and noise;
Symptoms of nasal congestion, nasal throat, dry lips and skin, hunger, fatigue and headache.
They also pointed out whether they didn\'t sleep well or too little the night before and whether they liked to work on the day of the VA.
The scale is marked. The VA-
Scales are managed by teachers who teach children how to use scales by example.
In a classroom at school, 2-
2 in experiment 2EF, VA-
The experimenter put forward the scale (
Introduction of tasks in their performance)
Play the instructions in the pre-recorded CD.
Results obtained on VA-in performance analysis
The scale was analyzed using a complete and incomplete design analysis. [
Figure 1 slightly]
35-measurement of sensory panel of perceived air quality
As described in Appendix B of ASHRAE standard 62, 39 adults were recruited to assess the air quality of the classroom. 1-
2007. Acceptable ventilation of indoor air quality (2007).
The subjects were mainly students under the age of 18.
At the age of 35, the proportion of women and men in each group is roughly equal.
They turned a blind eye to the conditions.
Different panels were used in experiment 1EF and 2ef.
Measure once a week, about 1-in the afternoon-1.
5 hours after the student leaves the classroom, the ventilation system is still running to avoid any disruption to normal school activities.
The group enters the classroom every 2-1 times
Three minutes in groups of two. to-
Three times at a time and immediately assess the air quality;
During these assessments, the doors are closed and the assessment order is balanced.
During the assessment, the team members lived in a well.
Ventilation hall close to classroom or outdoor.
The panel was transported between schools by bus.
Air quality was assessed by team members using four scales: continuous acceptability scale (Wargocki 2004)
Scale of odor intensity (Yaglou et al. 1936)
And two levels of VA-
Describe the balance of fresh and dry air in the classroom.
Statistical analysis of Shapiro
Wilk\'s test is used to determine if the rest is distributed properly and if necessary the data will be deletedtransformed.
When the normal hypothesis is met, the student is subjected to a repeated measurement 2x2 ANOVA, and the data is available under all four conditions of Experiment 1 EF.
For all available data, a generalized linear model of the sum of squares of the V-type is also used, even for students who do not have data in some cases. Friedman two-
When the normal hypothesis is not satisfied, and for the markers on VAscales, the method of non-parametric ANOVA is used.
Matching of Wilkersonpairs signed-
When the normal assumption is invalid, the grade test is used to analyze the main effects of running the electrostatic air purifier and filtration conditions (
Wargocki and WHYN 2007a, 2007a).
In experiment 2EF, The Wilcoxon test is always used to test the differences between the conditions, first for each school, and then for urban schools and rural schools, respectively, collect data from these two schools in each location category, and finally gather data from all schools.
In order to check whether the average performance of all tasks is showing a significant trend, pairing-
A wise comparison with the Wilcoxon test, using a group average of performance data for all students calculated for each task in either of the two cases: operate/or filter new/used. TheP-
The reject level of the zero assumption is set to 0. 05 (2-tail).
Results The classroom conditions measured in the physical measurement experiment were shown as inTables 3 and 4.
They show the temperature, RH ,[CO. sub. 2]
And the estimated effective ventilation rate is not affected by the intervention, while operating an electrostatic air purifier can consider reducing the concentration of particles in the air.
For classrooms with lower outdoor air supply rates, the impact is greater.
The operation of the electrostatic air purifier also reduces the amount of dust precipitation;
In Experiment 1 EF, this effect is more obvious. In experiment 1 EF, the outdoor air supply rate of the classroom is the lowest (Table 3)
Inconsistency in experiment 2EF (Table 4).
In experiment 1EF, exchanging the old filter with the new filter has no consistent effect on the particle concentration or the amount of dust deposited (Table 3).
The airflow speed of experiment 1EF is below 0. 14 m/s (27. 6 fpm)
The noise of the student\'s absence is ~ 36-44 dB(A);
Both quantities are different under experimental conditions.
The measurements in performance figure 2 summarize the results of the complete design analysis that examined the impact of operating an electrostatic air purifier on how students can complete the tasks presented to them in the experiment.
Due to teacher error in experiment 1EF, no subtraction, multiplication and number checking tests were performed in the fourth week of a class, no logical reasoning was performed in the first week of a class, sound insulation-
Reading was not carried out in one class during the first and second weeks.
Therefore, it is impossible for these tasks to repeat the measurement analysis in a complete 2x2 design.
The analysis of differences between the other two or three conditions, excluding the conditions for missing a class of data, is based on incomplete design;
As an indicator of performance, after adjustment (least square)
Means were used.
There is no analysis of the differences between single conditions, as in the current design they are confused with any differences between the weeks used by external factors or a gradual change in performance during the experiment.
The analysis of the performance impact shows that the operation of the air purifier has no consistent effect on the speed of performing different tasks.
In experiment 1EF, the operation of the air purifier significantly improves the speed of reading and understanding tasks (P