--- title: "Control strategies for indoor air quality" subject: "Environment and Pollution Control" chapter: 3 key: "semester_7/environment_and_pollution_control:indoor-air-control-strategies" source: https://www.bctengineer.com/q/semester_7/environment_and_pollution_control/indoor-air-control-strategies site: BCT Engineering --- # Control strategies for indoor air quality Environment and Pollution Control · Chapter 3: Indoor Air Quality - Asked in: year not given, 6 marks - Video: [How to Improve Indoor Air Quality? | How to Reduce Indoor Air Pollution?](https://www.youtube.com/watch?v=XkGyeHHM-oo) — Healthmania - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/environment_and_pollution_control/indoor-air-control-strategies - Whole chapter: https://www.bctengineer.com/md/semester_7/environment_and_pollution_control/chapter-3 ## Question Explain the main strategies used to control indoor air pollution. ## Short answer The main strategies are source control, ventilation and air cleaning. Source control, by eliminating or substituting pollutants, is most effective; ventilation supplies fresh outdoor air; air cleaning with filters or adsorbents supplements the other methods. ## Answer Three basic strategies are used, in order of effectiveness: source control, ventilation, and air cleaning. #### 1. Source control (best and most economical) - **Eliminate** the source, e.g. ban smoking, use only lead-free paints, avoid asbestos. - **Substitute** with low-emission products: low-VOC paints, formaldehyde-free boards, electric or LPG stoves. - **Modify** the source: seal radon entry cracks, enclose asbestos, let new furniture off-gas outdoors, and vent combustion appliances outside through flues and hoods. - Keep humidity below 60% to prevent mould, and fix leaks. #### 2. Ventilation - **Natural:** windows, vents, and the stack effect. - **Mechanical:** exhaust fans in kitchens and toilets; supply and exhaust fans with heat recovery. - Supply enough outdoor air per person according to ventilation standards (for example, 8-10 L/s per person is typical). - Place the air intake away from outdoor pollution (traffic, exhausts). #### 3. Air cleaning - **Particle filters:** fibrous filters, HEPA filters (99.97% of 0.3 $\mu$m particles), electrostatic precipitators. - **Gas removal:** activated carbon adsorption for VOCs and odours. - Cleaners treat only part of the air and do not remove all gases, so they supplement the other two methods. #### Other measures - Regular maintenance and cleaning of HVAC systems, testing houses for radon, carbon monoxide detectors, and good housekeeping (wet cleaning, no dust traps). ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which control strategy is the best and most economical? A. Air cleaning B. Source control C. Mechanical ventilation D. Detectors Answer: B. Eliminating, substituting or modifying the source is most effective; ventilation and air cleaning follow. (Key point: Order of strategies) 2. Which is an example of source modification? A. Fitting a HEPA filter B. Sealing radon entry cracks or venting combustion appliances outside C. Opening windows D. Using activated carbon Answer: B. Modifying the source includes sealing radon cracks, enclosing asbestos and venting appliances by flues. (Key point: Source modification) 3. HEPA filters remove: A. Gases such as VOCs B. 99.97% of 0.3 um particles C. Radon D. Odours only Answer: B. HEPA filters are particle filters rated at 99.97% for 0.3 um; gases need activated carbon. (Key point: HEPA filters) 4. Why are air cleaners only a supplement? A. They treat only part of the air and do not remove all gases B. They create ozone always C. They need no maintenance D. They replace ventilation Answer: A. Cleaners cannot treat all air or all gases, so they supplement source control and ventilation. 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