Indoor Air Quality Overview Reference

Why this matters

Indoor air quality (IAQ) affects customer's health + comfort. Many service calls relate to IAQ - allergies, asthma, mold, odors. The tech who understands IAQ basics + remediation can help customers significantly. This is the field card.

What IAQ involves

Air quality factors:

• Particulate matter (dust, pollen, dander)
• Volatile organic compounds (VOCs)
• Carbon dioxide
• Carbon monoxide
• Mold spores
• Humidity
• Temperature

Health impacts:

• Allergies
• Asthma triggers
• Respiratory irritation
• Sometimes long-term concerns

Common IAQ issues

Particulates:

• Dust
• Pollen
• Pet dander
• Smoke
• Construction debris

VOCs:

• New furnishings (off-gassing)
• Paint
• Cleaning products
• Building materials

Mold + mildew:

• Damp areas
• Health risk
• Smell

Combustion gases:

• CO (lethal)
• NO2
• Combustion equipment

Humidity:

• Too high (mold)
• Too low (dryness)

Stale air:

• Inadequate ventilation
• CO2 buildup
• Comfort issues

IAQ assessment

Customer reports:

• Allergies worse at home
• Headaches
• Fatigue
• Respiratory issues
• Smells / odors

Investigate:

• Sources
• Equipment
• Ventilation
• Identify root cause

Testing options

Particulate counter:

• Counts particles per volume
• Identifies high particulate
• Sometimes filterable; sometimes not

CO2 monitor:

• Ventilation indicator
• Above 1,000 ppm = inadequate ventilation
• 400-600 ppm = good

Humidity / temp:

• Hygrometer
• Comfort range 30-50% RH
• Above 60% mold risk

CO detector:

• Safety device (mandatory)
• Diagnostic during HVAC service

VOC meter (specialty):

• Total VOCs
• Sometimes specific gases
• Less common

Mold testing (specialty):

• Air sample to lab
• Spore identification
• Use specialist

Common IAQ improvements

Source reduction:

• Remove pollutant source
• Most effective
• Sometimes simple

Filtration:

• Equipment upgrade
• Per filtration article
• Higher MERV

Ventilation:

• Mechanical OR natural
• Fresh air introduction
• Sometimes ERV / HRV

Humidity control:

• Whole-house humidifier / dehumidifier
• Per humidity article

UV light (HVAC):

• Coil sterilization
• Air-stream UV
• Per UV article

Air purifiers (standalone):

• Single-room
• HEPA filtration
• Optional add-on

Source identification

Trace customer's symptoms to source:

At home (symptoms worse):

• Indoor source
• Investigate

Better away from home:

• Indoor IAQ issue likely
• Identify pollutant

Worse during specific activity:

• Cooking (range hood inadequate)
• Cleaning (chemical sensitivity)
• New furniture / paint (off-gassing)

Seasonal patterns:

• Allergens (pollen)
• Heating season (combustion)
• Cooling season (mold)

Customer's health considerations

Family member with:

• Allergies
• Asthma
• Respiratory disease
• Multiple chemical sensitivity

Higher IAQ standards needed:

• More filtration
• Source reduction
• Sometimes specialist consultation

Common HVAC IAQ improvements

Filter upgrade:

• Higher MERV (11-13)
• More frequent change
• Significant improvement

UV light:

• Coil sterilization
• Reduces mold
• Standard add-on

Duct cleaning (sometimes):

• Heavy buildup
• Specialty service
• Customer's preference

Whole-house air cleaner:

• HEPA OR similar
• Equipment investment
• Significant filtration

Customer's mold situation

Visible mold:

• Find source (moisture)
• Address moisture
• Remediate mold

Small (less than 10 sq ft):

• Customer can DIY (with caution)
• N95 mask + gloves
• Bleach OR specialty product

Larger:

• Professional remediation
• Specialty contractor
• Don't disturb until properly equipped

Customer's allergy customer

Common improvements:

• Filter upgrade
• HEPA whole-house OR room
• Duct cleaning (sometimes)
• Reduce pet dander (cleaning)
• Humidity control

Customer may also need:

• Medical advice (allergist)
• Lifestyle modifications
• Air purifiers

Common service request

Customer with allergies / asthma:

• "Can my HVAC help?"
• "What can I do for IAQ?"
• "Should I clean my ducts?"

Recommend:

• Filter upgrade first
• Source reduction (pet dander, etc.)
• Humidity control
• Sometimes equipment upgrade

Duct cleaning controversy

Effectiveness varies:

• EPA: not routinely recommended
• Sometimes beneficial (visible mold, rodent, major contamination)
• Sometimes minimal benefit

Customer's situation:

• Heavy buildup visible = consider
• New construction debris = consider
• Routine = often not needed

Customer education

For each customer:

• IAQ basics
• What you observe
• Recommendations
• Customer's choices

Specific scenarios

Customer's child with asthma:

• IAQ priority
• Multiple improvements
• Discuss with allergist sometimes

Customer's "musty smell" reported:

• Mold likely
• Investigate sources
• Address

Customer's new home off-gassing:

• Ventilation increased
• Time (off-gassing reduces)
• Air purifier

Customer's pet allergies:

• Filter upgrade
• Regular cleaning
• HEPA in problem rooms

Combustion equipment IAQ

Gas equipment:

• CO testing
• Combustion analysis
• Vent integrity

Wood-burning:

• Particulate
• Cleaning frequency
• Air sealing

Cooking:

• Range hood essential
• Vented outside
• Customer education

Outdoor air quality impact

Customer's indoor affected by:

• Local air quality
• Pollen seasons
• Smoke (wildfires)
• Industrial nearby

Limited control:

• Filtration helps
• Time-of-day windows
• Sometimes air sealed

Ventilation balance

Too little ventilation:

• Pollutants accumulate
• CO2 builds
• Stale air

Too much ventilation:

• Energy loss
• Outdoor pollutants enter
• Sometimes humidity issues

Right amount:

• Per ASHRAE 62.2
• Modern tight homes need mechanical

ERV / HRV systems

Energy / Heat Recovery Ventilator:

• Fresh air in
• Stale air out
• Heat exchange between
• Energy efficient

For tight homes:

• Required code sometimes
• IAQ benefit significant
• Capital investment

Smart sensors

IAQ monitors (consumer):

• CO2
• VOC
• Particulate
• Sometimes mold
• Customer awareness

Cost vs benefit:

• Customer's interest
• Sometimes diagnostic value
• Customer's choice

When to refer specialist

For:

• Comprehensive IAQ audit
• Mold remediation (large)
• Asbestos / lead
• Severe symptoms
• Sensitive customer

Specialists:

• IAQ consultant
• Mold remediation
• HVAC IAQ specialist
• Sometimes medical

Customer's home age impact

Newer construction:

• Tighter (better insulation)
• More mechanical ventilation needed
• Off-gassing common (new materials)

Older homes:

• Leakier (more natural ventilation)
• Old materials sometimes hazard (asbestos, lead)
• Different IAQ approach

Cross-trade IAQ observations

Two things stop work regardless of trade: a CO alarm sounding or symptoms consistent with CO exposure, and a gas odor. Get people out, ventilate, and call it in. Suspected asbestos or lead in material you are about to disturb also stops work until it is tested or handled by someone licensed for it.

Past those, every trade in the house walks past IAQ evidence the homeowner cannot interpret. The value is in reporting it.

Plumbers see the water side of every mold problem: supply leaks inside walls, a sweating cold line in a closed space, a trap that has dried out and is venting sewer gas into a room, a water heater in a closet with no combustion air, and the classic slow toilet or tub leak that has been feeding a subfloor for a year.

Electricians are in attics, crawls, and wall cavities more than anyone. They see bath fans terminating into the attic instead of outdoors, dryer ducts disconnected under a house, insulation that is wet or compressed, rodent contamination, and daylight through the envelope at every penetration they open.

HVAC techs own the largest share of the evidence: filter condition and bypass, standing water in a drain pan, biological growth on a coil, ducts pulled apart in an attic, a return in a garage or a mechanical closet pulling contaminated air into the house, and a system that never runs long enough to dehumidify.

Roofers and siding crews find the leak paths that feed hidden mold, and blocked soffit or ridge venting that turns an attic into a moisture trap.

Appliance techs find dryers venting into crawls, disconnected or crushed dryer duct, and range hoods that recirculate rather than exhaust.

Cleaners notice what recurs: dust that returns within days, a musty smell that comes back after every cleaning, condensation on windows in winter, and stains reappearing in the same corner.

Pest control sees droppings, nesting material in ducts and insulation, and the moisture conditions that attracted the pest in the first place.

Remodelers and flooring installers open the walls and floors where everything above finally becomes visible.

The working rule: you do not have to diagnose it, you have to report it. Photograph what you saw, note the location, write it plainly in the job notes, and tell the homeowner which trade should look at it. A note that reads "bath fan duct is disconnected in the attic over the hall bath, photographed" is worth more to the customer than any air test, and it is how a service company turns an incidental observation into the next job for someone on the team.

References

• EPA Indoor Air Quality resources
• ASHRAE 62.2 (Ventilation Indoor Air Quality)
• ASHRAE 55 (Thermal Environmental Conditions)
• AAFA (Asthma + Allergy Foundation)
• Manuall internal: Indoor Air Quality Testing, Common HVAC Add-Ons