Effectiveness of various ventilation systems in reducing exposure to biomass related particles: A real-life experiment


Background: Exposure to indoor air pollution, in particular particulate matter from biomass-fueled fires, has been identified as a major public health problem. Here, we test the effectiveness of simple ventilation systems in reducing concentrations of particulate matter in a standard experimental kitchen, built of traditional materials in Kenya. Materials and Methods: Continuous sampling for total particles, particulate matter <10 μm and <2.5 μm were sampled in a purpose-built rural kitchen using four ventilation scenarios: no ventilation, open window, open window and chimney and chimney only. The levels of pollutants were recorded and the effectiveness of different ventilation scenarios in reducing the exposure was compared. Results: For each size of particle, any type of ventilation showed a decrease in concentrations (P < 0.001), compared to the unventilated scenario of 70% or more. The lowest concentrations were observed when only a chimney was used; opening a window did not significantly alter the effectiveness of the chimney. Additionally, the changes in pollutant levels over time showed the least variation and lowest mean values when a chimney only was used. Conclusions: Simple ventilation systems, especially installation of a chimney, proved to be effective in significantly decreasing the exposure to biomass fuel-related indoor particulate matter exposure. The application of such technology may help in tackling this important public health issue.

Keywords: Environmental exposures, environmental monitoring, indoor air quality, public health, respiratory tract disease, rural communities

How to cite this article:
Majdan M, Svaro M, Kralova Z, Muendo RM, Taylor MS. Effectiveness of various ventilation systems in reducing exposure to biomass related particles: A real-life experiment. Ann Trop Med Public Health 2015;8:45-9
How to cite this URL:
Majdan M, Svaro M, Kralova Z, Muendo RM, Taylor MS. Effectiveness of various ventilation systems in reducing exposure to biomass related particles: A real-life experiment. Ann Trop Med Public Health [serial online] 2015 [cited 2020 Sep 19];8:45-9. Available from: https://www.atmph.org/text.asp?2015/8/3/45/157625

Acute infection of the respiratory system (ARI) is one of the world’s leading causes of burden of disease. [1] Exposure to indoor air pollution, in particular particulate matter from biomass-fuelled fires has been identified as a major public health problem, being a contributor to such infections, especially in low- and middle income countries (LMIC). [2],[3] It has been estimated that at times such diseases have been responsible for almost one third of all deaths among children under 5 years of age, and the majority of these deaths are concentrated in LMIC. [4] The possibility of synergistic co-infection between human immunodeficiency virus and acquired immune deficiency syndrome (HIV/AIDS) and respiratory disease, is also a cause of additional concern in areas of high HIV/AIDS prevalence such as the LMIC of sub-Saharan Africa. [5] Non-infectious lung conditions, such as chronic obstructive pulmonary disease (COPD) have also been linked to the use of biomass fuels. [6] It has been estimated that 80-90% of rural households in LMIC rely on biomass (i.e., combustible wood or charcoal, other plant material such as crop residues, and animal dung) as the primary source of household cooking fuel, [7],[8] and in some parts of the world the reliance on biomass is increasing. [9],[10]

When used in open fire or simple small-scale devices, biomass fuels emit a variety of potentially hazardous airborne pollutants. Especially relevant to these noted health problems are respirable smoke particulates, [11] which have been linked to deleterious effects on health, in vitro and/or in vivo.[12] There are a number of reasons concerning environmental sustainability and economic factors, [8],[13] as well as health, that reductions in the use of biomass fuel might be encouraged. [8] However, even where other fuel sources are currently available, poverty and increasing population sizes in LMIC mean a large, and in some cases increasing, number of people are still reliant on biomass for cooking. [14] In such situations where alternatives are limited, then practical means to reduce human exposure to the harmful effects of such smoke might be sought. There is some evidence that different cooking methods, e.g., the use of improved stoves, can reduce the amount of harmful smoke released during combustion, with associated reductions in adverse markers of health. [14] Reducing smoke exposure by use of a stove with an integral chimney has been shown to reduce lung irritation and CO exposure in a randomized controlled trial. [15] A similar cooking system was shown to reduce particulate exposure and blood pressure, [16] and was associated with a non-significant trend towards reduced risk of low birth weight, when given to pregnant women in a LMIC setting. [17]

Here we show the design of a simple physical, whole-room ventilation system, in the form of a chimney made of locally-available materials, and test its effectiveness in reducing concentrations of particulate matter in a standard experimental kitchen built of traditional materials in Kenya.

Materials and Methods

Study setting

The presented study had an experimental design and was conducted in a controlled environment. All measurements took place in a kitchen that has been built specifically for the study in the town of Kwale in Kenya’s Coastal Province, which was designed to mimic real life kitchens in the study region. It was entirely built by local craftsmen from usual building materials and the size has been derived from an earlier field study conducted in the region. Within this previous study 125 kitchens were sampled overall and the mean size was used for the model kitchen in the present study: 3.5 m × 2.2 m and 2.5 m in height at its highest point.

Design of the study

For the purpose of the measurements and to achieve the study goals, four different scenarios were created by adjusting the experimental kitchen:

Scenario 1

Under this scenario the kitchen was sealed and no openings were present on the roof or on the walls. The door has been partially open. This opening was 15 cm and was used in the same manner under all other scenarios; the main reason for it was to allow basic oxygen inlet for the fire. This scenario was used as the “worst” and served as a reference for comparison with other scenarios.

Scenario 2

Under scenario 2, a window of a size 70 cm × 40 cm was built into one of the walls. When measurements were conducted under this scenario, the window stayed open.

Scenario 3

A simple chimney was designed and built for this scenario. When sampling under scenario 3, the window has been sealed and the chimney was the only outlet.

Scenario 4

This scenario was a combination of scenarios 2 and 3, which included the use of the chimney along with opening the window.

Sampling protocol and equipment

A standardized sampling protocol was designed and applied under the four scenarios to allow for comparisons. A fire has been built on the same site in all samplings using the same amount of wood from the same type of tree. The sampling equipment was placed on the same spot in the approximate breathing zone of an adult person sitting or kneeling by the fire. All equipment was turned on once the fire started to burn. No persons were present in the room while the measurements went on. A 60 min log of instant concentrations of particles was recorded. Concentrations have been recorded in 5 s intervals, and thus a total of 700 readings were collected for each sampling. First, total particulate matter was sampled followed by sampling of PM10 and PM2.5. The sampling pump rate was set to air flow of 2.2 Litres/min. To measure dust and its individual fractions the Casella Microdust Pro 880NM with a size selective dust adapter and filters for PM10 and PM2.5 was used.

Data analysis

The main line of analysis in this study is a side-by-side comparison of concentrations of different types of particles under the four scenarios. To describe the levels of pollution means with corresponding 95% confidence intervals were calculated for each type of particles and each scenario. Additionally a 60 min log of concentrations for each sampling has been evaluated by graphical comparison. Changes in concentrations under the four scenarios were evaluated by calculating percent of mean concentration decrease compared to the reference sampling for which in case of all particle types the sampling in the sealed kitchen was taken. One-way analysis of variance (ANOVA) was used to compare means between the scenarios. A P < 0.05 was considered statistically significant. The R statistical software was used for all analyses and graphics for this paper.


The recorded measurement from all experimental scenarios show that indoor fires of the type typically used for cooking in this area produce substantial amounts of particulate air pollution. The highest observed values were of larger particles, predominantly PM10, and this appears to contribute most to the TPM values.

Significant differences in mean concentrations of the four types of sampled particles were observed. [Figure 1] presents a comparison of mean values of particle concentrations across all time points, along with 95% confidence intervals. In case of all size of particles (total, PM 10 and PM 2.5) levels were the highest when the kitchen was sealed. Any type of ventilation meant a decrease in concentrations (P < 0.001 tested by ANOVA). Of the types of ventilations applied, the lowest concentrations are observed when only a chimney was used. Opening a window did not significantly alter the effectiveness of the chimney.

Figure 1: Mean levels of particle concentrations of various sizes with CI95% under the four different scenarios of sampling

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Using the sealed kitchen as a reference, [Table 1] presents changes of concentration under the four scenarios. Using solely a chimney decreased the concentrations most significantly in case of PM10 and PM2.5, whereas the decrease of TPM levels was similar under all three scenarios. In all cases the decrease was statistically significant (P < 0.001).

Table 1: Percentual change of mean concentrations of the sampled types of particles under the four scenarios

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Logs of the samplings are presented for each type of particles and all four scenarios in [Figure 2], [Figure 3], [Figure 4], showing in all scenarios the inevitable variability in levels of indoor air pollution produced by a complex chemical system, such as burning wood. In general, reflecting the patterns of mean levels, the highest peak concentrations were observed when the kitchen was sealed. Under this scenario levels showed the highest variations with relatively sudden increases and drops in particle concentrations especially in case of TPM. The least apparent variation was observed in PM2.5. The variation over time was less apparent in all other scenarious showing the most stable pattern and lowest mean values when a chimney only was used.

Figure 2: Log of variation of concentration of total suspended particles during 1 h monitoring under the four scenarios of sampling

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Figure 3: Log of variation of concentration of particles sized <10 μm during 1 h sampling under the four scenarios
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Figure 4: Log of variation of concentration of particles sized <2.5 μm during 1 h sampling under the four scenarios
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We have investigated the effectiveness of a locally-made and affordable chimney, which might be proposed as a way to reduce people’s exposure to indoor air pollution. The results suggest that this form of ventilation is effective in reducing indoor smoke concentrations, and possibly even more effective that other ventilation in the form of an open window.

The analysis of mean values suggests that any type of ventilation helps lowering the concentration of particles of all sizes as compared to sealed kitchen, with potential to reduce the exposure of anybody present to harmful particles. [18] It has been noted the use of simple and locally acceptable technologies, such as that described here, is a valuable part of the solution to those health problems seen in LMIC which are linked to exposure to indoor smoke. [19] When comparing having a chimney installed with having a window open, the chimney serves the purpose better. Opening a window in a room which already has a chimney appears to show no additional improvement. Thus, of the four scenarios tested here, the use of a chimney appear to be the best solution.

Second, based on the variation of concentrations during 1 h of continuous sampling we see much higher variations when the kitchen is sealed compared to any type of ventilation. Some variation is present when ventilation is used, and that is likely to be the effect of changes in air currents and circulation, caused by momentary changes in the outdoor environmental wind speed or direction. Although this may be seen to reduce the similarity of the different scenarios, as this was an experimental design approximating a real-life situation, such behavior is to be expected in real life, too. A strength of this project is that all observations were obtained in a real-life setting, using a purpose-built kitchen which was similar in design and material construction to that which is typically used by local people.

Additionally, we showed that without ventilation the fire is likely to show greater variability in levels of particulate matter produced, possibly as the lack of ventilation affects oxygen levels, and heat and/or flame levels fluctuate. These fluctuations, which would be expected based on laboratory work carried out in more controlled conditions [20] can cause sudden increases of exposure to particulate pollution (when the fire dies) followed by decreases (after flames start again). Thus, they are more likely to be exposed to extremely high levels in the short-term.

This research fits within the wider context of our understanding of indoor air pollution. From previous studies, we know that the majority of previously sampled 125 real kitchens had no window or chimney ventilation. [21] Therefore we can imply that under normal current circumstances the person (usually women) doing the cooking, and other inhabitants are exposed to much higher levels of particles than they would, with the provision of ventilation of any type. Other research groups have shown that the provision of improved stoves can reduce indoor air pollution, with consequent reductions in blood pressure of those cooking, [16] and a meta-analysis has shown that reduced exposure to indoor air pollution is also associated with reduced risk of suffering infectious lung disease, such as tuberculosis. [22]

Particulates of the PM2.5 to PM10 range, as studied here, are not the only emissions of biomass fire of relevance to human health. [12] Further work, in which samples might include NOx and CO, would be of interest to verify the effect of improved ventilation on human exposure to harmful emissions.


This study was funded by an institutional grant obtained from the faculty of Health Sciences and Social Work of the Trnava University in Trnava, Slovakia. We are grateful to local craftsmen in Kwale for their help in building the experimental kitchen for this study and to local community members for their help and guidance in recreating real-life cooking and living situations.

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Source of Support: This study was funded by an institutional grant obtained from the Faculty of Health Sciences and Social Work of the Trnava University in Trnava, Slovakia, Conflict of Interest: None


DOI: 10.4103/1755-6783.157625


[Figure 1], [Figure 2], [Figure 3], [Figure 4]


[Table 1]

Paul Mies has now been involved with test reports and comparing products for a decade. He is a highly sought-after specialist in these areas as well as in general health and nutrition advice. With this expertise and the team behind atmph.org, they test, compare and report on all sought-after products on the Internet around the topics of health, slimming, beauty and more. The results are ultimately summarized and disclosed to readers.


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