Indoor Air Quality Questions and Answers

Answer: C

Occupants generate it at a fairly predictable rate, so its steady concentration above the outdoor value reflects the outdoor air supplied per person. It says nothing about sources unrelated to people, which is the usual misreading of the measurement.

Answer: D

The organism multiplies in warm stagnant water and is inhaled as an aerosol from towers, showers and humidifiers. Control is by temperature management, avoiding stagnation and periodic disinfection rather than by air treatment.

Answer: A

Correct answer: Managing moisture and repairing water damage

Moulds, bacteria and dust mites all require water, and it is the one requirement a building can be made to withhold. Nutrients are present everywhere in dust, timber and plasterboard.

So control means fixing leaks, ventilating moisture at its source, insulating to prevent condensation and drying wetted material quickly - within a day or two, before growth establishes. Raising the temperature or the lighting does nothing, and killing surface growth without removing the moisture simply invites its return.

Answer: B

Filtration efficiency has a minimum near that diameter because larger particles are caught by interception and impaction while smaller ones are caught by diffusion. Rating a filter at its worst case guarantees performance everywhere else.

Answer: C

Adsorption on the carbon surface captures organic vapours, and the bed must be replaced once saturated or it will release what it holds. It does essentially nothing for particles, which is why combined units carry a separate particulate stage.

Answer: D

Correct answer: Fine particulate and carbon monoxide

Burning wood, dung or crop residue on an unvented stove releases both in large quantities into the room, and kitchen concentrations of fine particulate reach hundreds or thousands of micrograms per cubic metre - far above any ambient standard.

The exposure falls on women and small children, who are present during cooking, and it is among the largest environmental health burdens worldwide. Radon comes from soil, formaldehyde from furnishings and ozone from equipment; none is the biomass problem.

Answer: A

Any device with a high voltage corona can generate it, and so can ozone-emitting air cleaners sold as purifiers. It also reacts with indoor organics to form irritating secondary products, so it is a poor thing to add deliberately.

Answer: B

Intact bonded asbestos releases very few fibres, so undisturbed material in good condition is usually managed in place. Drilling, sanding or demolition is what releases respirable fibres, which is why removal is a controlled operation.

Answer: C

Because the contaminated warm plume rises above the occupied zone and is extracted at ceiling level, the breathing zone sees air closer to supply quality. It works well for heat and buoyant contaminants and poorly for dense ones released at low level.

Answer: D

Correct answer: The source point is fixed

Local exhaust captures the contaminant at the point of release, before it disperses into the room, so a hood can be placed close to it and a modest flow suffices.

A moving source defeats that, since the capture velocity falls rapidly with distance from the hood and a hood cannot follow. Dilution is then the only option, and it needs far more air for the same protection. Room size is not the criterion, and a harmless contaminant needs no local capture at all.