| Boiling Point No. 02 - Special Edition April 1991 |
by Maria Nystrom, Lund Centre for Habitat Studies, Sweden
"Then Mr Biswas had another surprise. Through the doorway at the far end he saw the kitchen. The kitchen had mud walls and it was lower than the hall and appeared to be completely without light. The doorway gaped black; soot stained the wall about it and the ceiling just above; so that the blackness seemed to fill the kitchen like a solid substance."
There are projects disseminating stoves with chimneys. However, a chimney on its own cannot solve the problem of smoke and soot in the kitchen. Window and door openings influence air movements which affect the draught in the chimney. The kitchen can spread smoke, humidity and unpleasant odours to the rest of the dwelling even if the stove has a chimney.
Mr Biswas's surprise is the daily reality of women in the third world. Smoke and soot are perhaps the major inconveniences, but there are also problems with heat radiation, high temperatures and damp, especially in countries with a warm and humid climate. The question is, how can we build better kitchens and dwellings to avoid problems such as smoke and pollution and offer people a healthier indoor environment? A contribution to the answer might be a better understanding of the systems concerned: the cooking system, the kitchen system and the dwelling system. How do they function separately and together?
Cross Ventilated Kitchens and the Placement of Stoves
The outdoor climate - temperature, humidity and prevailing winds - is of major importance because it will influence the kitchen and dwelling design and especially the placement of window and door openings and the stove. For example, cross ventilation is necessary for good indoor climate in warm and humid zones (tropical climate), but in some sub-tropical zones there are also cold and wet winters, and the strategy is to seal the house during this period.
The rules are different again for a desert climate. In summer the house should be well insulated and closed during the day to keep out hot air, and opened to cool air at night; In the winter when the days are warm and the nights are cold, the principles are lots of ventilation during the day and a closed house at night.
The figures below show that the stove and the chimney should be placed where there is less air movement (shaded area). If there is a dining table, it should be placed where the ventilation is good.
Experiences from a kitchen and stove project in Nicaragua also showed that the movement of air is different in a room with bamboo walls that act as filters from that in a room with solid brick walls.
Why Not Chimney Hoods?
A lot of work has been done with fixed chimneys on stoves, less on the chimney hood. But there are reasons to consider the chimney hood, particularly where portable stoves without chimneys or with short chimneys are used indoors ea. family preference, uncertain fuel supplies.
The most effective way is perhaps to use the chimney hood in combination with a stove equipped with a fixed chimney and where possible the kitchen should preferably be separated from the rest of the dwelling to avoid transfer of the moisture, heat and soot produced in the kitchen to other rooms.
Sooty and poorly ventilated kitchen huts are a favourable milieu for mould; with little air movement and fats in soot as nourishment. .