Indoor Air Quality Questions and Answers

Answer: A

A source releasing at a given rate into a room reaches a far higher steady concentration than the same source outdoors, because the diluting volume and the air exchange are both small. Tightening buildings for energy efficiency made the effect worse rather than better.

Answer: B

Radon is generated by the decay of radium in soil and rock and is drawn in through cracks and service penetrations by the slight negative pressure a heated building maintains. Building materials and water contribute far less in most houses.

Answer: C

Radon itself is inert and largely exhaled again, but its solid decay products attach to airborne particles, lodge in the bronchial epithelium and irradiate it with alpha particles. That is why the working level, not the radon concentration alone, describes the dose.

Answer: D

Urea-formaldehyde resins in particle board, plywood and medium density fibreboard release the gas slowly for years, and the rate rises with temperature and humidity. Emission falls roughly exponentially as the material ages.

Answer: A

Any fuel-burning appliance short of air produces it, and an unvented or blocked flue delivers it straight into the occupied space. Because it is colourless and odourless the first warning is usually a symptom rather than a smell.

Answer: B

Hundreds of compounds are present at once, usually at low individual concentration, which is why the total volatile organic compound figure is often quoted. New or newly refurbished buildings show the highest levels and decay over months.

Answer: C

Correct answer: Relative humidity

House dust mites have no means of drinking; they absorb water vapour directly from the air through their cuticle. Below about 50 per cent relative humidity they cannot maintain their water balance and the population collapses.

That makes humidity the practical control, and it is why mite allergen is a lesser problem in dry climates and at altitude. Temperature matters only within the range that already suits them, and light and carbon dioxide have no bearing on their survival.

Answer: D

Sidestream smoke from the smouldering tip dominates the mixture and is generated at a lower temperature, so it is richer in many toxic species per unit of tobacco burnt. It carries thousands of compounds including several known carcinogens.

Answer: A

It is the volumetric ventilation rate divided by the room volume, so a rate of one means the room volume is replaced each hour. It sets the dilution available to every indoor source and appears in the steady state mass balance directly.

Answer: B

Sick building syndrome describes a cluster of non-specific complaints such as headache, irritation and fatigue with no diagnosable cause. Building related illness names conditions with a definite agent and diagnosis, such as legionnaires disease or hypersensitivity pneumonitis.