Smoke Hoods

Overview

According to the World Health Organization (WHO) as many as 1.9 million people die each year as a result of indoor air pollution (IAP).  The overwhelming cause of this pollution is inefficient und poorly ventilated cooking and heating with solid biomass. Smoke hoods are an excellent alternative to alleviate the dangers related to smoke from open fires as they draw the smoke out of the house. This makes the indoor air much cleaner and healthier.

What is a Smoke Hood

installed smoke hood, Practical Action

Smoke hoods consist of a main stove body, from which a flue takes the polluting gases out of a house through the roof. In many ways they can be matched to the traditional fireplaces or improved cookstoves (ICS) found in households all over the world for cooking, boiling water, lighting or heating. In hot regions, a hood made of insulating material can take away much of the heat out of the kitchen. In cold regions, the hood can be built to allow the family to benefit from the radiant heat of the fire. In both cases the hood can allow for smoking of meats or other ritual or traditional uses of an open fire.

Impacts

The installation of a smoke hoods can be extremely effective in  improving the air quality in houses. This applies especially, when traditional biomass burning stoves are being used without a chimney. In addition, some efficient stoves may not be clean and therefore employing a smoke hood allows for health benefits coupled with lower operating costs. Moreover, in some cultures, an open fire plays a special social role as a place around which the  family gathers, traditional meals are cooked or other important rituals. As a result the introduction of improved cookstoves is difficult and a smoke hood serves as the best alternative for improving indoor air quality.

Concurrently, although the health impact can be significant, the environmental impact is not necessarily reduced because - methane and other greenhouse gas (GHG) emissions are not as dramatically reduced with a smoke hood as with an efficient cookstove. However smoke hoods can also be integrated with lower-cost, locally made, more efficient cook stoves that, combined with a well-designed smoke hoods can reduce IAP up to 80%.

Target Group

Families which are currently cooking on open fires with biomass or charcoal are the target group for smoke hoods. Specifically those families that for cultural or other reasons do not wish t or are unable to adopt an improved cookstove. This is especially the case in regions where an open fire is used for heating or smoking purposes.  And, in circumstances where low-cost efficient (but not clean) cookstoves are available, a smokehood can be combined as an integrated system to both improve efficiency and reduce indoor air pollution (IAP) at optimal cost and offering the users the greatest comfort, flexibility and overall cost-benefit.

There are different traditional and practical reasons, why people are cooking on open fires:

• People are used to cook on open fires
• People are very poor and wood and agriculture residues are for free
• Other or cleaner technologies and fuels are not available or not affordable
• It is cold and the fire is also used for space heating
• Traditionally the family is sitting around the fire
• The smoke kills vermin in the thatched roof
• Users wish to smoke meats or fish

The smoke hood technology may not be a good solution for every culture or region. The potential for an adequate cost / benefit, user acceptance and subsequent impact of introducing smoke hoods in a given setting are affected by several criteria.

Those that lead to a positive scenario include, but are not limited to the following:

• No alternative options that might have a greater combination of benefits than smoke hood
• Generally simple pot cooking is practiced
• Users reject other improvements due to cultural or other reasons
• Internal dimensions that allow the cook to use familiar cooking practices
• Biomass and charcoal are used by the majority
• Materials and production skills within the community exist to produce the hoods locally
• Certain level of manufacturing possibilities is available like bending
• Access to necessary raw materials like sheet or recycled metals
• Good transport networks that allow hoods to be entirely or partially manufactured elsewhere
• Access to small-scale credit funds

"Healthy Hoods" Project

Healthy Hoods by Practical Action and BSH

Although basic designs for smokehoods had been tested in the past, their effectiveness usually remained at around 60% smoke reduction and therefore below WHO standards.  However, Bosch and Siemens Home Appliances Group (BSH) together with the Universität der Bundeswehr München and Practical Action (PA) with support from the Deutsche Entwicklungs Gesellschaft (DEG) have recently developed and improved design that removes over 80% of the smoke and meets WHO standards.

To make the technology as accessible as possible, the project is developing an interactive website.  The website, www.healthysmokehoods.org offers anyone the opportunity to start the process of designing their own smoke hood. 

By providing basic data on the type of region, household size, cooking pots and habits and special needs, a customized design complete with manufacturing instructions will be generated. A film showing the impact of the hoods is available on the web: http://www.youtube.com

Lessons Learned

Earlier work on smoke hoods by Practical Action led to very well-accepted hoods in Kenya, Nepal and Tanzania. These hoods did not remove as much smoke, but they illustrate that smoke hoods are appropriate across a wide range of cultures and types of climate.

Kenya

In Kenya, the well-known low-cost upesi stove is built under the hood in place of the open fire. The upesi is a well accepted ceramic stove which can be built into a base, with the hood set over the top to provide a neat safe environment – reducing the risk of burns and reducing the fuel costs. Another type of stove, built on a principle called a ‘rocket’ stove, is becoming very popular. This could be combined with a smoke hood, with the stove reducing emissions and fuel costs, and the smoke hood venting any residual smoke up the smoke hood. The smoke hood is sufficiently versatile to allow these changes to happen.

Tanzania, Uganda

A successful initiative in Tanzania and Uganda involves the use of smoke hoods, combined with the installation of upesi stoves.

Some structural changes included removing a wall across the door opening, and the addition of two small windows. The result is that the Maasai homes in this district have been transformed from enclosed smoke-filled kitchens to clean bright open houses.

The very low level of emissions now evident in the households is partly to do with the technology, but also perhaps because of the extreme fuel shortage. Women in this region walk for several hours twice or three times per week to gather fuel.

Key to all of this is the combination of stove and hood, and the fact that the stove can be designed to fit many shapes and sizes of stove, including locally manufactured stoves that save a lot of fuel, but may not get rid of sufficient smoke to make them healthy. Putting a smoke hood on top of such a stove allows local manufacture of a stove+hood combination that reduces pressures on forests, reducing the harmful emissions within the households, and can all be locally manufactured.

Smoke Hood Manufacture

Manufacturing of smoke hoods, Practical Action

Smoke hoods need to be made within certain tolerances, but these are not so critical as for successful chimney stoves. The hoods can be made by local artisans, thus providing new employment, and support if ever things go wrong.

Smoke hoods can be made in a variety of sizes; the website tool advises on the right size for a particular situation. It provides dimensions and drawings for hood manufacture. If more than one size is feasible, thought should be given to the size of hood that will minimize wastage of steel, as the dimensions should not be substantially modified once the size is chosen.

The smoke hoods currently being made in Nepal are being made only with hand tools. Steel sheet is brought into the area as flat sheets, and the cutting and seaming is done by hand by skilled craftsman trained by the project team, and by one of the first entrepreneurs trained by the project.

Costs - Can people afford smoke hoods?

Smoke hoods are quite expensive if you are on a very low income. However, the major problem is finding all the money at once – the up-front or capital costs. Once installed, the technologies often save fuel costs for reasons described above. One way to enable purchase of hoods is to create revolving funds. These funds are based on seed capital – an amount of money that starts off the process. A few households belonging to a community group, will buy the appliance in instalments; sometimes paying a low additional interest rate to provide a small income for the person running the fund. Once they have paid back some of the money, this provides enough funds for a few more people to get appliances. The larger the seed capital, the sooner everyone gets a chance to reduce smoke in their kitchen.

Further Information

• Project Homepage: Healthy Smoke Hoods / Practical Action
• Smoke Hood Designer (by Practical Action and BSH)
• Chimney Stoves and Smoke Hoods - technical brief by Practical Action)
• Homepage Bosch Siemens Homeapliances Group
• Heating - Indoor Air Temperature
• Design Principles for Wood Burning Cook Stoves Bryden.M. et. al. Aprovecho Research Center 2004
• The effect of ventilation on carbon monoxide and particulate levels in a test kitchen Still, D. & MacCarty, N.  in Boiling Point 51,  Practical Action 2006
• Smoke, Health and Household Energy Volume 1: Participatory Methods for Design, Installation, monitoring and assessment of smoke alleviation technologies. Bates. E. et. Al. Practical Action May 2005
• Smoke, Health and Household Energy Volume 2: Researching pathways to scaling up sustainable and effective kitchen smoke alleviation. Bates. E. et. Al. Practical Action May 2005
• Good website for looking at efficient and effective stoves: http://www.crest.org/discussiongroups/resources/stoves/
• HELPS International
• How to Build The Improved Household Stove: A Construction Manual for the Rocket – Lorena and Shielded Fire Stove, Ministry of Energy and Mineral Development, Uganda.
• World Health Organisation website on indoor air pollution

References

This article is basically based on experiences, lessons learned and information gathered by Bosch and Siemens Home Appliances Group (BSH) together with the Universität der Bundeswehr München and Practical Action with support from the Deutsche Entwicklungs Gesellschaft (DEG).