METHODS OF IMPROVING INDOOR AIR QUALITY

    There are three main methods of decreasing and/or preventing indoor air pollution from cooking activities.


                                 1.    By producing less smoke: improved stoves, improved fuels and fuel switching

                                 2.    By removing smoke from indoors: chimneys, flues, hoods and ventilation
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                                 3.    By reducing exposure to smoke: changes in cooking practices and behavior, and kitchen design


1. Producing Less Smoke

Improved Stoves

One of the most traditional forms of cooking in the lesser developed world is over three stone open fires. This form of cooking can cause poor indoor air quality by producing high amounts of particulate matter and carbon monoxide.

 Improved stoves can reduce air emissions by:

Types of Improved Stoves

There is no one single way to make an improved stove, numerous improved stoves have been designed and manufactured throughout the world. Figure 1 is a Estufa Justa stove utilized in Latin America. Many other stoves follow this basic concept.

Figure 1: Estufa Justa Stove
Figure 1: Estufa Justa Stove Basic Concept

Most stoves are built with an opening for fuel which is located below a hole or place for a cooking pot. In the stove above, the chimney like elbow in which the fire is made creates a draft which increases combustion efficiency.  More surface area is heated by placing the cooking pots in the holes and less heat is lost to the surroundings due to insulation. This can increases cooking efficiency by decreasing the amount of fuel needed and the time spent cooking. Stoves like this can be made out of many materials including earth, clay, brick, ceramic and metal. Another variation on this stove concept can be seen in Figure 2 below.
 Figure 2: Plancha Stove
Figure 2: Plancha Stove

Additional Information on Improved Stoves

Much more information is available on emissions reducing and fuel efficient stoves on the Additional Resources and Links page.

Improved Fuels and and Fuel Switching

    Despite the kind of stove, there are various kinds of fuels that can be used for cooking. The amount of particulate matter and carbon monoxide produced depends highly on the type of fuel used. Figure 3 ranks various fuels based on emissions.

Figure 3: Emissions Comparison of Fuels
Figure 3: Emissions Comparison of Fuels [1]

Emissions are an important element in choosing a fuel but they are not the only deciding factor. Cost and availability of the fuels also needs to be considered. For instance, according to Figure 3 petroleum has the lowest emissions but it is not a renewable resource and is not always readily available in developing countries as well as it can be quite costly. For these reasons using alternative or improved fuels is often the most difficult way of reducing indoor air quality.


2. Removing Smoke from Indoors

Chimneys, Flues, Hoods and Ventilation [1]

    Improving the efficiency and emissions of the stove in one method of improving indoor air quality. Another method of improving indoor air quality is by removing the smoke produced by the stove to the outside. This does not eliminate the pollution but removes it from the home where it can cause the most damage. There are several ways of removing the smoke.


Chimneys and Flues
    Chimneys and flues are integrated into the design of the stove allowing the smoke to exit to the outdoors. The placement and angle of chimney and flues varies between stove designs. Chimneys and flues that remove the smoke directly from the combustion chamber straight upwards provide a draft that increases efficiency. Chimneys and flues can be constructed out of clay, cement, bricks, ceramic or metal. However, one issue with chimneys and flues is their relatively high cost. Also if not placed properly smoke can return through windows and doors. But if they are affordable and properly designed, chimneys and flues can greatly improve indoor air quality.

Hoods

    Hoods work in much the same way as chimneys and flues however they are structurally independent of the stove. This can be a benefit because they can work with many types of stoves including open fires while still removing a good portion of the smoke. Hoods, however, still have the problem of cost and also their size can be cumbersome especially in small homes.

Ventilation
    Improved ventilation can be another method of removing smoke from a home. The proper placement of windows and doors can greatly increase the flow of air through a home and thus improve the removal of smoke. This could be the cheapest and simplest method of removing smoke from a home, however maybe not the most efficient. Also, cultural feelings toward open windows and doors must be taken into consideration.

More information on chimneys, flues, hoods and ventilation can be found at the web sites recommended on the Additional Resources and Links page.

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3. Reducing Exposure to Smoke

Changes in Cooking Practices and Behaviors:   

    Changes in cooking practices and behaviors can reduce exposure to smoke by either limiting the amount of time inhabitants are exposed or by setting up situations where inhabitants are distanced from the smoke.
               
    Ways of limiting the cooking time/exposure time include the preparation of food before lighting the fire so that the fire is used more efficiently, pre-soaking the foods in water, and using any insulating containers available to keep food warm. However, there can be many obstacles to these kinds of actions and changes. Soaking and insulating might not be common practice in certain areas and may require significant changes to cooking customs.1

    Changes in household cooking behavior can be partially effective in decreasing exposure to smoke. This is better then no change if no technical solution is available. Some of these changes can seem relatively easy, such as simply keeping children away from the fire, but are in reality much more complicated. Continuing with the "just keep child away from the fire" idea, if the only adult that is the children's caretaker is also the cook, as in many cases, then to not keep them near the cook and thus the fire would open the children to other dangers. Keeping in mind the complexity of some of these issues, a partial list of behavioral changes that could improve indoor air quality includes, increasing education about the harm of air pollution so that the inhabitants can know to avoid being too close to the smoke if possible, bettering management of the cooking space to decrease time spent close to the fire and bettering decision making involving a balance between air pollution problems and other dangers. Another point to make here is that the ability of the individual responsible for cooking  will greatly affect even technological solutions.

Changes in Kitchen Design:

     Another main action, whether corrective or preventive, that can be used to reduce exposure is the redesign of the kitchen set up. Kitchen redesign goes hand in hand with ventilation concerns since a potential redesign could influence locations of doors, windows, and furniture. The other main change that could improve air quality in the home is placing the source of the smoke nearer to any windows, or other more open spaces in the room. Care must be taken because for many homes the most open location in the kitchen may be the center and placement of the fire there could lead to pollution concentrations.  Another redesign that can drastically reduce exposure is to locate the kitchen in a separate room. The problem of this solution would be that it might be socially and physically unacceptable if not difficult to accomplish.

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1.    Budds, J., Biran, A. & Rouse, J. “What’s Cooking: A review of the health impacts of indoor air pollution and technical interventions for its reduction.” WELL,         LSHTM/WEDC: England, 2001.