Publications·December 31, 1998
This field manual, prepared by GTZ’s Household Energy Programme with WHO, explains simple, low-cost techniques to measure indoor air pollution and combustion quality in households and small establishments that burn biomass and other solid fuels. It is written for practitioners in developing countries—engineers, health officers, stove programs, NGOs—who need robust methods that work under tough field conditions and do not depend on expensive lab equipment or uninterrupted power. The motivation is stark: heavy reliance on wood, dung, crop residues and coal in stoves—often without chimneys—creates very high concentrations of pollutants that drive respiratory disease, especially among children; the manual argues that practical standards and fit-for-purpose monitoring are essential to verify progress and protect health.
Core concepts and definitions you can use in the field
The manual starts by defining key terms—emissions (what the source releases), concentration (what’s in the air), exposure (what a person breathes), and dose (what enters the body)—and lists the principal pollutants from household combustion: CO, hydrocarbons (VOC/PAH), NOx, SO₂, soot/particulates, and formaldehyde. It distinguishes emission monitoring (near the source or in chimneys) from exposure monitoring (in the breathing zone), highlighting different objectives, sampling locations and durations.
Because pollutant clouds from cooking fires spread in characteristic ways, the manual shows how diffusion, convection, air flow and building geometry shape concentrations; it recommends sampling at breathing height of the cook and explains when to use short-term vs. long-term measurement windows.
Combustion basics tied to what you measure
A short primer on biomass combustion links fuel properties, stove design, and operation to pollutant formation. For practical diagnostics, the manual suggests using a CO/CO₂ ratio: values ≪ 0.1 (e.g., 0.02) indicate comparatively complete combustion; it also lists typical emission factors for fuelwood stoves (e.g., ~44 g/kg CO, 10 g/kg total hydrocarbons). Measuring O₂ helps estimate excess air and flue losses, which tie back to efficiency.
How to measure—step by step, with rugged options
1) Emission measurements (chimney and open-fire)
For stoves with chimneys, place probes between stove and stack to read CO, total hydrocarbons (CnHm), CO₂ (for fuel conversion), and optionally O₂ (for normalization to a reference oxygen). Also record flue temperature and draft.
For open stoves, there is no “standard” duct, so you can either use a hood or sample in the main exhaust stream (around pot height). Avoid artifacts: cool the gas stream before CO/O₂ sampling (to condense steam), but heat the line for hydrocarbons so condensable tars remain airborne as aerosols.
2) Exposure measurements (what the cook breathes)
Place samplers at mouth–nose level; in small kitchens and huts, pollutant plumes often form an ellipsoid from the source, shaped by temperature, ventilation, humidity, and room volume/height. Choose integrated (average) or grab/spot (maxima) strategies depending on your objective.
3) Instruments you can actually carry and maintain
The manual emphasizes two inexpensive workhorses:
Colorimetric tubes (short- and long-term, active with hand pumps or passive diffusion collectors) for CO, CO₂, NO₂, SO₂, HCHO and total hydrocarbons. They’re pre-calibrated by the manufacturer and read by color-length; you can extend range by increasing strokes and correct readings for pressure/altitude (the manual provides the conversion). [Sections and methods cataloged in Chapter 5].
Gravimetric PM using filters + portable pumps, with mass concentration computed from pre/post filter weights and sampled volume:
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For a rapid proxy of soot/tar from solid-fuel exhausts, it documents the Baum/Bacharach spot method: draw a fixed gas volume through filter paper with a hand pump (often ~10 strokes), visually compare stain gray/yellow/brown tone to a chart (expanded to 100 shades), and infer total carbon (mg/m³). Even slight visible staining at 10 strokes signals seriously high TSP.
The manual also catalogs electronic gas detectors (CO, CO₂, NOx, SO₂, O₂) for real-time reads, stressing span-gas calibration and the trade-offs: higher upfront costs and sensitivity to heat/dust/power vs. instant data.
Practicalities that determine data quality
A full chapter covers test preparation (site description, fuel, stove type, cooking tasks, season, timing), calibration (gas sensors and air pumps), and field protocols to capture both average and peak exposures during the heat-up, full burn, and cool-down phases of cooking—where peaks often occur when adding fuel. It also includes checklists, field forms, and basic statistics for sampling.
Standards and using results for decisions
The manual situates field measurements within WHO guidelines (acute and chronic limits for CO, NO₂, SO₂, O₃, particulates, etc.), and explains TLV-TWA, STEL, Ceiling concepts—useful when adapting or proposing national standards or program acceptance criteria (e.g., for improved stoves). It cautions that where concentrations are far above limits (often 10–100× in traditional kitchens), simple methods are appropriate and more sensitive instruments may be impractical or misleading in harsh field settings.
Why this manual is still a go-to reference
It bridges engineering and public health: linking combustion diagnostics (CO/CO₂, O₂, flue temperature, draft) to human exposure in kitchens.
It democratizes measurement: colorimetric tubes, modified Bacharach stains, filter + pump gravimetry—techniques that field teams can learn in days, not months.
It prioritizes QA/QC under constraints: calibration, altitude/pressure corrections, weighing discipline, and fit-for-purpose sampling so your numbers are defensible.
Used as intended, this manual helps programs verify clean-cooking benefits, rank stove designs, identify hot spots in kitchens and optimize training and behavior change—with enough rigor to inform policy, standards, and scale-up.
Keywords
Indoor air pollution; biomass stoves; CO/CO₂ ratio; gravimetric PM; colorimetric tubes (active/passive); diffusion collectors; Bacharach soot/tar method; chimney & open-stove sampling; breathing-zone exposure; calibration (span gas, pump); QA/QC; simple field protocols; WHO guideline context.