" Used air" during class
- Poor air quality in classrooms
There are many factors during a lesson that can influence the learning of our children is positive but also negative. For example, in discussions in recent months, the lighting in the classroom as a possible starting point to create an optimum environment for the students. A literature search on this subject showed that the brightness (illuminance) in the classroom a more important influence on the concentration and the willingness to learn than the type of illumination (conventional lighting or full spectrum light).
When asked what other factors adversely affect the attention and affect the learning ability of students is the indoor air quality at a very high priority. After reviewing the relevant literature it became clear that air quality exercises during lessons in the classes an even more significant impact than the previously discussed parameters. This is essentially also the subjective perception of students and teachers who frequently "stale air" to the extreme state at the end of an hour complaining. It is not surprising that the concentration is already significantly impaired before the subjective perception of "bad air".
review on air quality in rooms from the newspaper DIE ZEIT
Right? Fug is tiring
Is it true that "stale air" in a stuffy room a lower oxygen content than fresh?
We know this: Many people are sitting in a room together, and after an hour uses a yawn. "Let but sometimes pure oxygen," cries, then somebody, and the windows are open.
But it is not the lack of oxygen, which makes us tired and possibly not even the foul-smelling fumes of others. »Used air" is characterized primarily by a higher percentage of carbon dioxide, and that makes us tired in very small quantities. When we breathe, we enrich the air with CO2 to: In the normal room air for about 21 percent oxygen and only 0.03 percent CO2. Our breath, however, contains only 14 percent oxygen, but 5.6 percent carbon dioxide - the amount of which has thus more than a hundredfold. And from only 2.5 percent CO2 air is considered toxic.
I once had a bill drawn up, what happens when ten people are in a 60-cubic-meter room that is hermetically sealed. The modeling breathes in every human being eight liters of air per minute, and again, every so hours per about half a cubic meter. The entire amount of oxygen has very little influence - after an hour, the O2 content in the air decreased from 21 to 20.3 percent. But the carbon dioxide content has increased more than tenfold, from 0.03 percent to 0.5 percent. As though no one dies, but it beats again clearly well-being. to assess
CO2 concentration as a measure of indoor air quality
order to indoor air quality, the provision has proven the CO2 concentration. The normal concentration of CO2 in ambient air is 360 ppm (parts per million) in clean air areas and about 500 ppm in urban areas. The many studies underlying Limit of 1,000 ppm, the so-called "Pettenkoffer number". This value is still considered by many experts as an important target for a still sufficient indoor air quality (3, 5). The also frequently cited value of 1500 ppm (Air Hygiene value, DIN 1946-2) is not synonymous with freedom problem in terms of indoor air quality. At 1500 ppm CO2 about 35% of the passengers' dissatisfaction with the type of indoor air quality (1). For this reason, CO 2 concentrations of \u0026lt;> are changing how the air quality in the course of instruction?
In classes without ventilation and windows closed, the CO2 content is increasing in the Rauluft in the course of a Lesson at an average of 1500 ppm (1). Depending on the initial value, ie depending on the ventilation activity in the previous break, and depending on the number of pupils, as the levels at the end of the session 1900-3300 ppm (5 schools of different types) (2). Many hours of lessons with the windows closed out at the usual room occupancy rates in the course of the morning to CO2 levels of 5000 ppm (5). After just one double-hour, despite at times open door reaches values of 1980 ppm (5). Two studies from the USA confirm these numbers: In 9 schools, of which there were no prior complaints about poor air quality, CO2 concentrations were 400-5000 ppm, the conductivity of 1000 ppm in 74% of all the rooms was exceeded (3). In the second study from Michigan, the values were 2700-3300 ppm (4). The CO2 concentrations, which were documented in the schools will, most likely no acute health risk; they do, however, are an important indicator of air quality and point out that the exchange of air in the vast number of classes is woefully inadequate. Due to the lack of air exchange occurs in addition to the CO2 in a temperature increase, an increase of humidity and perspiration from clothing, furniture and building materials. Investigations in niedersäsischen schools confirm these figures for Germany and document that in the course of the day (9 - 15 clock) due to poor ventilation activities during breaks and free periods, the CO2 concentration increases steadily and stabilized over 14 clock at critically high levels of 5000 ppm ( 1). The
these numbers as representative of the situation in many schools can apply the very matching conditions make the study with the reality apparent in many schools. Were investigated classrooms of the 5th Classes with an average occupancy of 27 students and a similar pause length:
In 7 niedersäsischen Schools was determined at 58 days, the CO2 concentration in the air (1). In summer 32% of the measurements were above the air quality of 1500 ppm (DIN 1946-2), in winter were, however, 89% of measurements above the limit. The following quote from the publication of this study very accurately characterizes the situation in many classrooms: "... the measurements were made at a cool outdoor weather in 5th grade, who from 9:50 -15:45 clock instruction CO2 values. ppm were at the course starts at about 800. Before the end of the first lesson of the DIN-value is already exceeded 1500 ppm. ventilation activity in the intervals are hardly noticeable ... "
conflicts arise especially if the energy savings in the heating season brings to the fore. Even taking into account the climate, the objectives are not preventing ventilation, but goal should be a demand-based ventilation. With inadequate ventilation facilitated by the increase in humidity, the mold growth.
Under what conditions is it most frequently on the situation "inadequate air quality"?
ventilation deficits thus arise mainly in the cooler season. At lower temperatures, the indoor CO2 levels are generally higher, due to further reductions in air activities. Additionally, it is mentioned that a lack of air quality not only on some days in winter occurs when at subzero temperatures, the windows are opened, as not so good, but that again shows the investigation from Lower Saxony, in 87% of days of teaching is unsatisfactory air quality was present (1). It should also increase, the maximum CO2 values, depending on the age of the students, ie, the situation in the older grades are worse than anticipated (1).
What kind of ventilation is necessary to keep the air quality in classrooms in the range of acceptable values?
It is a fallacy to believe that sufficient eg 2-3 window to "tilt" during a short break to keep the air quality within an acceptable range (7). However, these minimum ventilation activity is still better than the often observed situation that absolutely no windows are open.
The frequently practiced night ventilation (windows in tilt) results, especially for large spaces to the fact that not all parts of the space uniformly supplied with fresh air. The air exchange in this type of ventilation is also low (0.8 -4 / h). Significantly, however, the effective cross-ventilation (40 / h), 0.5 / h means that replaced half of the room air per hour, 4 / h means that within an hour the air is completely replaced 4 times. Inadequate ventilation
activities, for example by only a few open windows to tilt in the breaks, lead to rule-firm in the course of the school day CO2 concentrations are reached which are leistungsbeeinträchtigend (1, 5). As these changes meet usually in late morning with further disturbances (loss of concentration ability due to general tiredness or lack of food intake) is not significantly decreasing willingness of students to lunch unexpectedly.
In recent weeks, the air operations in a 6th Class at a high school documented by sampling. It was found very conflicting results: In about 40% of the observed lessons were open at any moment the window. A satisfactory ventilation activity with the windows open during and after the lesson was in a further 40% of the classes are documented. In the remaining 20%, at least at the end of the lesson was aired. When entering a technical room, the windows were closed after the break very often. To a regular airing, especially in the big breaks to ensure the appointment of an air service would certainly useful (13).
The consequences of "bad air"
addition to a decreased concentration and increased fatigue may have a further negative consequences of poor air quality. From epidemiological studies are available the first evidence that high indoor CO2 concentrations with increased absenteeism of the students are associated. Indoor CO2 levels at the end of the hour in the middle of 1300 to 1400 ppm lead to a rise in absenteeism by 10 - 20% (12). A recent study (11) provides evidence, as will be very adversely affected the academic performance of children from defective air quality. For example, a significant Relationship between air quality and the result of a math test described. The lower the ventilation, ie the air exchange in the classes, the poorer sections, students take the math test.
How much fresh air is necessary to create optimal learning conditions?
The higher air exchange rates positively affected the performance has been confirmed in several studies (8, 9). A recent study concludes that the largest performance gain is achieved when the ventilation rate is at least 15 liters per second per person (9). Some authors recommend for optimum performance Ventilation rates of 20 - 25 L per person per second (10). Can be regarded as the minimum fresh air per student should be 7 liters / sec. are (2) They say that in a classroom (volume 180 m3, 25 students) and in cool weather, the air exchange rate not 6.5 / h , Ie just below within 10 minutes. , the entire air space once have been replaced. If the windows are on tilt, a maximum air exchange rates of 5/Std. (Mean: 0.8 - 4/Std.) Realize. With half-opened windows to let exchange rates 10/hr. . Achieve These figures make it clear that under the gaze of a sufficient air quality winding the windows during the lesson would have to be on tilt. If the window because of very low temperatures or clearly perceptible noise remain closed during school hours is during the short breaks cross ventilation (exchange rate to 40/hour.) Necessary (7). As a consequence of these findings, the schools in most Scandinavian countries were consequently equipped with ventilation systems.
Conclusion
If we are concerned about the well being of children and ensure optimal learning conditions, it would improve air quality by regularly airing an effective and cost-effective measure in Compared to the installation of a full-spectrum lighting. The air quality in many classrooms, for example at Ohmoor High School in Niendorf, is due to a random survey on the ventilation activity and due to the similar conditions as in the case study schools in Lower Saxony considered most likely to be insufficient. Previous studies provide clear evidence that this unsatisfactory air quality could adversely affect the performance and well-being of the students (and teachers). To achieve the quality necessary for adequate air ventilation rates, the designation of an "air service" makes sense of it consider the possibility that both the small and large breaks in the short term will be provided by cross-ventilation for a sufficient supply of fresh air.
literature
first Grams, H. et al. Breathe in schools. Health Care 2003; 64: 447-456
second Kuiv, TA. Indoor climate and ventilation in Tallin school buildings. Proc. Estonian Acad. Sci. Eng, 2007;.
third 13:17-25 Daisey, JM. et al. Indoor air quality, ventilation and health symptoms in schools. Indoor Air, 2003, 13: 53-64
4th Godwin, C., Battermamm S. Indoor air quality in Michigan schools. Indoor Air, 2006 16: 459-473
5th Heudorf, U. Does the Passive House School the solution of spatial problems of hygiene in schools? Health, 2007; 69: 408-414
6th Kimmel, R. et al. Insufficient ventilation as a cause of mood disorders in a primary school. Health Care, 2000, 62: 660-664
7th Publication by the Lower Saxony State Health Department: Recommended ventilation of work environments (office and classrooms). http://www.nlga.niedersachsen.de/ (2nd edition September 2007)
8th Wakefield J. Environmental Health Perspectives, 2002, 110, (6): A298-305
9th Seppänen O. et al. Ventilation and performance in office work. Indoor Air, 2006, 16 (1): 28-36
10. Wargocki P., et al. Ventilation and health in non-industrial indoor environments (EUROVEN). Indoor Air, 2002; 12 (2): 113-128
11. Shaughnessy RJ. et al. A preliminary study on the association between ventilation rates in classrooms and student performance. Indoor Air, 2006; 16 (6): 465-468
12. Shendell DG. et al. Associations between classroom CO2 concentrations and student attendance in Washington and Idaho. Indoor Air, 2004; 14 (5): 333-341
13. Information des Niedersäsischen Landesgesundheitsamtes. Luftqualität und Raumklima in Unterrichtsräumen. www.nlga.niedersachsen.de/Schwerpunktthemen/Lufthygiene
Dr. med. Detlef Nachtigall
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