Chapter 22 Quiz
Multiple Choice
1. MERV stands for:
a) Maximum Efficiency Removal Value b) Minimum Efficiency Reporting Value c) Measured Exhaust Recirculation Volume d) Multi-Element Rating for Ventilation
Answer: b — MERV is an ASHRAE standardized rating (Standard 52.2) measuring how effectively filters capture particles of various sizes.
2. The primary risk of installing a MERV 13 filter in a system designed for MERV 8 is:
a) The filter will absorb moisture and become a mold source b) The higher rating will capture too many beneficial microorganisms c) Increased airflow restriction can reduce system performance and potentially damage equipment d) MERV 13 filters are only rated for commercial use and void residential equipment warranties
Answer: c — Higher MERV ratings mean denser media and higher pressure drop. In a system designed for lower resistance, this reduces airflow, can freeze evaporator coils in cooling mode, and can cause furnace heat exchangers to overheat.
3. A HEPA filter is rated to capture what percentage of particles at 0.3 microns?
a) 95% b) 99.0% c) 99.97% d) 100%
Answer: c — True HEPA standard requires 99.97% capture efficiency at the most penetrating particle size (0.3 microns).
4. Which of the following indoor air quality problems CANNOT be effectively addressed by HEPA filtration?
a) Pet dander b) Mold spores c) Volatile organic compounds (VOCs) from paint and furniture d) Pollen
Answer: c — HEPA filters capture particles. VOCs are gas molecules and pass through HEPA media unimpeded. Activated carbon adsorption is used for VOC reduction.
5. Ozone generators marketed as air purifiers are problematic primarily because:
a) They produce extremely loud noise during operation b) Ozone at concentrations effective against pathogens is harmful to breathe and reacts with VOCs to create additional pollutants c) They consume excessive amounts of electricity d) They only work for odors, not for biological contaminants
Answer: b — Ozone is a respiratory irritant, and at levels effective against pathogens, it exceeds safe breathing concentrations. It also reacts with household VOCs to form secondary pollutants including formaldehyde.
6. The EPA's estimated relationship between indoor and outdoor air quality is that indoor air is typically:
a) Roughly equivalent to outdoor air b) Cleaner than outdoor air due to filtration c) 2–5 times more polluted than outdoor air d) More polluted only in new construction due to off-gassing
Answer: c — The EPA estimates indoor air is 2–5 times more polluted than outdoor air in typical homes, because pollutants accumulate in enclosed spaces with limited dilution.
7. The target indoor relative humidity range of 40–60% is primarily driven by:
a) Human comfort preferences alone — lower humidity feels dry, higher feels muggy b) Balancing health, comfort, structural protection, and pest (mold, dust mite) control c) HVAC system operating efficiency — systems perform best within this range d) Building code requirements for occupied spaces
Answer: b — Below 40% RH: respiratory discomfort, wood damage, increased virus transmission. Above 60% RH: mold growth, dust mite proliferation, structural moisture damage. The 40–60% range optimizes across all these factors.
8. A whole-home bypass humidifier needs its water panel replaced annually because:
a) Modern humidifiers are designed with planned obsolescence b) Mineral deposits from the water calcify the media and biological growth can occur in the warm, wet environment c) The water panel loses its ability to control humidity levels due to chemical breakdown d) EPA regulations require annual replacement of all HVAC water components
Answer: b — The warm, wet humidifier environment is ideal for mineral buildup and biological growth. Annual replacement prevents these from degrading humidifier performance and creating air quality problems.
9. CO detectors in a residential home should be placed:
a) Near the floor, since CO is heavier than air and settles downward b) Only in rooms with combustion appliances c) On every level and within 10 feet of each sleeping area d) In a central location such as the main hallway, regardless of floor
Answer: c — Code requirements and best practice call for detectors on every level and near each sleeping area. CO distributes fairly evenly in air and does not strongly stratify by height.
10. When a CO alarm sounds in your home, the correct first action is:
a) Find and turn off the combustion appliance you suspect is causing the problem b) Open windows to ventilate the space c) Get everyone out of the house immediately and call 911 from outside d) Check whether family members have symptoms before deciding whether to evacuate
Answer: c — Immediate evacuation, no exceptions. CO exposure can cause confusion and impaired judgment that makes symptoms an unreliable guide. Never investigate the source from inside the home; that is the job of emergency responders.
Short Answer
11. A homeowner is considering upgrading from MERV 8 to MERV 13 filters for better air quality. What questions should they ask before making this change, and what alternatives might achieve better filtration without the airflow risks?
Model answer: They should check: (1) What MERV rating does the equipment manufacturer recommend? (2) Is the current system showing any signs of airflow restriction already? (3) What is the duct system's static pressure? Alternatives that provide better filtration without high pressure drop: a deep-media filter cabinet (4–5 inch thick media at MERV 11 has far lower pressure drop than 1-inch MERV 13), a whole-home media air cleaner, or a portable HEPA unit in the most important room. The thick media option provides high filtration efficiency with acceptable airflow restriction and is the most practical whole-home solution.
12. Explain why radon is the most underappreciated serious indoor air quality hazard, and why many homeowners who spend money on air purifiers have never tested for it.
Model answer: Radon is the second leading cause of lung cancer in the US (21,000 deaths/year), is odorless and colorless, and cannot be detected by any air purifier or filtration system. A $15–$30 test kit can detect a life-threatening hazard; mitigation if needed costs $800–$2,500 and works reliably. By contrast, air purifiers address particulate and odor complaints that are inconvenient but rarely life-threatening in typical homes. Homeowners buy purifiers because they respond to visible, sensory cues (dust, odors) and because purifier marketing is everywhere. Radon has no sensory presence and no consumer marketing infrastructure. The health risk/dollar comparison strongly favors radon testing, but the awareness gap means most homeowners have never tested.