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Hoods and Chimneys to Reduce Indoor Air Pollution from Wood and Coal Fires

Boiling Point
Front cover of Boiling Point issue 35
Issue 35 (1995) How Much Can NGO’s Achieve
ArticleHoods and Chimneys to Reduce Indoor Air Pollution from Wood and Coal Fires
AuthorNguyen Trong Phuong
In Vietnam at present, up to 90 per cent of the population still uses wood or coal for domestic cooking. In recent years, the use of coal briquettes for domestic cooking has increased in Hanoi as costs of electricity and oil have increased. These fuels produce a lot of pollutants during their burning process, thus polluting the air in the kitchen and the whole house. The increasing use of coal briquettes inside dwellings has led to an increase in lung and respiratory diseases treated in the hospitals of Hanoi.

In 1992, the Vietnamese Ministry of Health issued new regulations on the maximum allowable concentrations of some pollutants as show in Table 1.

[top] [end]Chimneys and hoods

Chimneys and hoods are another means of evacuating smoke and other pollutants from the combustion process. The relationship between chimney height, hood dimensions and open area of the hood affect the amount of air removed. It was observed that when the height and other dimensions of the chimney remain unchanged, the changes in the open area of the hood greatly affect the rate of exhaustion. A decrease in the open area greatly increases the rate. However, changing the open area gives different results depending on whether it is done by changes in the vertical or horizontal dimensions. Horizontal dimensional decreases have a greater effect on smoke exhaustion than vertical decreases. Table 1: Vietnamese Ministry of Health regulations

Pollutant
Max Concentration
Living area
Max Concentration
Work place

Carbon dioxide (CO2)
0.1%
0.5%

Carbon monoxide (CO)
3 mg/m³
30 mg/m³

Sulphurous gases
0.5 mg/m³
20 mg/m³

Table 2: Cooking window - smoke removal

Type of fuel
Structure of hood
CO concentrations (ppm)
Kitchen
CO concentrations (ppm)
Bedroom
CO concentrations (ppm)
Outdoor

Coal briquettes
Hood with cooking window




Figure 1
5
4
2


Figure 2
26
19
2

Wood
Hood with cooking window


Figure 1
17
16
2


Figure 2
30
31
2

The structure of the hood also affects its capacity to remove smoke. The hood with a cooking window as seen in Figure 1 has a better exhaust effect than the type of hood shown in Figure 2. The results in Table 2 show the advantage of this type of chimney when tested in our experimental building.
Figure 1: Hood
Figure 1: Hood
Figure 2: Hood
Figure 2: Hood
Different types of stoves have different effects on indoor air pollution. An open fire does not completely burn all the fuel and so produces a lot of smoke, soot and pollutants. The use of improved stoves contributes to better burning efficiency and so helps to reduce the air pollution. Fixed stoves, with chimneys built into the kitchen, produce little smoke in the kitchen. Improved, portable stoves also need chimneys provide better combustion if used in the kitchen.

Although the measurements taken from these tests are of little normative significance, they indicate that the level of indoor air pollution depends on several factors such as room ventilation, chimney construction, hood design and the kinds of fuel used.

Extract from report of the Lund Seminar, April 1993. Nguyen Trong Phaong, Hanoi Architectural Institute and Lund Institute, Sweden

[top] [end]Contents: Boiling Point 35: How Much Can NGO’s Achieve

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Scaling Up NGO Impacts - From Chulo Group to NGO in Nepal - Women and Energy Project - Kenya - Senegal Stove Success Story - The Senegal Diambar Stove Project - NGO Poverty Projects Evaluated - NGOs - Whats Behind the Initials - The Zambia Charcoal Industry - Trees For Fuel - The Foresters View - Fuelwood - A South African View - Energy and the Household Environment in Accra - Hoods and Chimneys to Reduce Indoor Air Pollution from Wood and Coal Fires - Testing of Charcoal and Coal Briquette Stoves





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Page created: 20 August 2007; Last edited: 20 August 2007; Version: 1
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