How household fuels changed
Long ago, people burned dung cakes, crop waste and wood. Later coal and kerosene came into use. Then came LPG (liquefied petroleum gas) in cylinders and piped natural gas (PNG). Today many homes also use electric and induction cookers and solar cookers.
Each change followed a need: less smoke, faster cooking, less time collecting fuel, and less pollution. Money, where you live, and what is available in your area still decide the choice.
Comparing fuels: smoke and heat used
A good fuel burns completely, gives plenty of heat and makes little smoke. Solid fuels such as wood and dung burn badly in simple stoves. They make smoke, soot and carbon monoxide.
Efficiency means the share of heat that reaches the food. Typical values are only rough: open wood fire about 10%, coal about 15%, kerosene about 45%, LPG about 60%, induction about 85%. Higher efficiency saves fuel, money and time.
Safe use of gas fuels
LPG is mixed with a strong-smelling chemical so you can notice leaks. LPG is heavier than air, so it collects near the floor. Piped natural gas (mostly methane) is lighter than air, so it rises.
If you smell gas: 1) do not light a match or press any switch, 2) open doors and windows, 3) close the regulator or gas valve, 4) leave and call for help. Check joints with soapy water: bubbles show a leak. Keep the cylinder upright and turn the regulator off at night.
Safe use of solid and liquid fuels: carbon monoxide
When there is too little air, fuel burns incompletely and makes carbon monoxide (CO). CO has no colour or smell, and it stops the blood carrying oxygen. Never burn coal, charcoal or wood in a closed room, and never run a generator indoors.
Keep a vent or a chimney. Keep kerosene in a closed container away from children. For electric cookers: dry hands, no damaged wires, and a proper plug.
How to run a small fuel survey
1) Ask a question: which fuels do families use, and why? 2) Make a short sheet: fuel, reason, smoke, cost, and safety. 3) Ask 10 families (with permission). 4) Count the answers in a tally table. 5) Draw a bar chart. 6) Write a clear conclusion and one suggestion. Keep names private and only share the totals.
Key formulas and definitions
- Efficiency = (heat reaching the pot / heat given by fuel) × 100%
- Fuel + oxygen → CO₂ + H₂O + heat (complete burning)
- Fuel + little oxygen → CO + soot + heat (incomplete burning)
Worked examples
1. A stove gives out 1000 kJ of heat and 600 kJ reaches the pot. Find the efficiency.
Efficiency = 600 / 1000 × 100 = 60%.
2. Why does a gas leak at home need windows opened but no switch pressed?
Open windows let the gas out. A tiny spark from a switch can light the gas mixture and cause a fire or explosion.
3. A family burns charcoal in a closed room at night. Which gas is the main danger and why?
Carbon monoxide. Little air means incomplete burning. CO has no smell and stops blood from carrying oxygen.
Common mistakes
- Using a match to look for a leak. Use soapy water instead.
- Thinking you will smell carbon monoxide. It has no smell.
- Believing a bigger flame means a better fuel. A clean blue flame is best.
- Forgetting that electric cooking is clean in the kitchen but the power may come from burning coal or gas elsewhere.