Indoor Air Quality Testing Reference

Why this matters

Customers report headaches, allergies, fatigue, musty smell, dust accumulation - and the cause is usually their indoor air. The HVAC or restoration tech who can measure + diagnose IAQ issues turns a vague complaint into a specific solution. This isn't about selling fear; it's about giving the customer what they actually need. This is the field card.

What "indoor air quality" actually means

Several measurable parameters, each with health + comfort implications:

Particulate matter (PM2.5, PM10): dust, pollen, smoke, soot. Measured in µg/m³. PM2.5 is the most concerning for health (small enough to penetrate lung tissue).

VOCs (volatile organic compounds): off-gassing from paint, new furniture, cleaning products, building materials. Measured in ppb or mg/m³.

Carbon dioxide (CO2): indicator of ventilation adequacy. Outdoor ~ 420 ppm; comfortable indoor < 1,000 ppm; > 2,000 ppm causes drowsiness.

Carbon monoxide (CO): from combustion. Deadly. Indoor should be < 9 ppm continuous; > 35 ppm action level; > 70 ppm urgent.

Humidity (RH): 30 - 60% comfortable + healthy. Outside this range = mold (high) or respiratory issues + static (low).

Temperature: comfort + indirect indicator of HVAC operation.

Radon: naturally-occurring radioactive gas from soil. Long-term exposure linked to lung cancer. EPA action level 4.0 pCi/L; mitigation often recommended above 2.0.

Mold spores: total counts + species identification. Some health risk; baseline outdoor varies seasonally.

Formaldehyde: VOC from pressed wood, some insulation. Tracked separately from total VOC.

Where IAQ issues come from

Combustion appliances (cracked HX, blocked flue, backdrafting → CO + NOx + soot). Building materials (new paint, flooring, particleboard → formaldehyde + VOCs; pre-1980 asbestos + lead). Water-damaged materials (mold growth). Pets + occupants (dander, fragrance). Outdoor infiltration (pollen, vehicle exhaust, wildfire smoke). Cleaning products (VOCs). Tobacco residue (third-hand smoke). Cooking (PM2.5 from gas stoves). Radon (ground-source through foundation).

Field instruments

Combustion analyzer: CO + CO2 in flue gas (standard HVAC tool; not direct IAQ measurement but identifies CO leaks).

CO alarm + monitor: standalone CO detector (per code) + handheld for diagnostic walk-around.

Multi-parameter IAQ meter (Temtop, AirVisual, Awair Element): PM, CO2, VOC, temperature, humidity in one handheld or fixed device. Quality varies; mid-tier consumer models are decent for diagnosis.

Professional IAQ instruments (TSI, Aeroqual): precise; commercial / industrial; calibration-traceable.

Manometer (for ventilation): differential pressure of supply vs return; bath fan flow.

Hygrometer: relative humidity at multiple points (more accurate than a single house-wide reading).

Radon test kit (charcoal canister 2 - 7 days OR continuous radon monitor): short-term screening or long-term detailed.

Mold sample kits (air sampling pump + tape lift): laboratory analysis required for species + counts.

Symptom-to-cause investigation

Customer reports symptoms; map symptoms to likely causes:

Headache + nausea + dizziness, particularly when heating system runs: suspect CO leak. Immediate CO test + furnace combustion analysis.

Allergies worse indoors than out: dust + pet dander + mold. Filter audit + humidity check + mold inspection.

Musty smell: moisture + mold. Find the moisture source.

Stuffy / drowsy in the bedroom: ventilation inadequate. CO2 elevated. Bedroom door closed + no transfer + no fresh air = CO2 builds overnight.

Static + dry skin in winter: humidity too low (often 15 - 20%). Whole-house humidifier or point-of-use.

Sticky / clammy + AC running but feels humid: oversized AC short-cycles; insufficient dehumidification. Variable-speed equipment OR supplemental dehumidifier.

New-construction or remodel + headaches: VOC off-gassing. Time + ventilation; sometimes activated carbon filtration helps.

Old home + child + cognitive concerns: lead paint exposure. Lead test + RRP-certified remediation.

Specific room with chronic illness pattern: site-specific (mold behind wall, hidden leak, attached garage CO bleed).

Test method by parameter

CO: combustion analyzer + ambient CO meter; check at appliance, in living space, near attached garage entry. Investigate any reading > 9 ppm continuous.

CO2: handheld meter over time; map readings by room. Bedrooms with closed doors typically highest.

PM2.5/PM10: handheld meter + reference period. Compare to outdoor baseline; identify sources (cooking, fireplace, smoking).

VOC: handheld meter; high readings near suspected source. Identify by ventilation challenge (open windows + retest).

Humidity: 30 - 60% target. Hygrometer at multiple locations + at different times of day.

Radon: long-term test (90+ days) is most reliable; short-term screening (3 - 7 days) for quick check. Test kit to certified lab.

Mold: visible inspection first; air sample only if no visible source. Compare indoor to outdoor counts. Above 5x outdoor = contamination indication.

When to recommend mitigation

CO present: stop work, evacuate if elevated; emergency repair of source (cracked HX, blocked flue, backdraft); install/replace CO alarms.

PM/VOC high: source reduction (no smoking, change cleaning products); add filtration (MERV 13+ media filter, HEPA in problem rooms); ventilate.

Humidity high: dehumidifier, fix water source, improve ventilation in wet rooms.

Humidity low: whole-house humidifier (in heating climate) OR point-of-use (room).

Radon elevated: SSD (sub-slab depressurization) system; certified radon mitigator.

Mold: covered in mold remediation basics.

Ventilation inadequate (high CO2): ERV / HRV install; per ASHRAE 62.2.

Customer education

No single test = full picture: IAQ has many variables; one snapshot doesn't catch them all. Comprehensive diagnosis takes time + multiple tests.

Source reduction beats filtration: cheaper + more effective to eliminate the source than to filter it after.

Recommendations are health-related: present findings without alarmism; recommend solutions in priority of health impact.

Refer when out of scope: certified IAQ assessors (BPI, IECC) for comprehensive analysis; industrial hygienists for complex cases.

What other techs do wrong

Selling "indoor air quality systems" without measuring first. Customer pays for a UV light or expensive filter system without diagnosis. The actual issue might be a cracked heat exchanger (urgent) or a bath fan venting into attic (different fix). Test before selling.

References

• ASHRAE 62.2 (residential ventilation)
• EPA Indoor Air Quality + Radon guidance
• IICRC S520 (mold)
• ACGIH (industrial hygiene guidance for limit values)
• AHRI standards for filtration
• Manuall internal: Mold Remediation Basics, Attic Moisture + Ventilation, Combustion Fundamentals