Indoor Air Quality (IAQ)

If eye irritation, headaches, or allergies began shortly after moving into a newly constructed building, the building's Indoor Air Quality (IAQ) should be suspected.

The WHO has defined this phenomenon as Sick Building Syndrome (SBS) since 1984, reporting that up to 30% of new and renovated buildings may be affected.

What Is Sick Building Syndrome?

SBS is a cluster of nonspecific symptoms that appear only while the occupant is inside the building. EPA Indoor Air Facts No. 4 lists headaches, eye/nose/throat irritation, fatigue, difficulty concentrating, skin irritation, and nausea as representative symptoms, and specifies that improvement upon leaving the building is the key diagnostic criterion.

When a specific pathogen or specific diagnosis is identified, it is classified not as SBS but as BRI (Building-Related Illness) — a separate category. The essential nature of SBS is "accumulation of multiple causal factors that cannot be attributed to a single source."

The key point is that perfecting any one factor will not resolve SBS. Four axes must be managed simultaneously — materials (VOC), microorganisms (mold), outdoor particles (PM), and ventilation (filters) — to pull cumulative risk below the threshold. The four H2 sections that follow represent the smallest first step for each axis.

The IAQ Four Axes at a Glance

The table below is a matrix pairing the four pollutant sources with their respective "minimum first-line actions." Use it when reviewing specifications or as a facility inspection checklist.

Managing just one axis well is insufficient; ignoring any one axis erodes the gains made in the others quickly. The sections that follow examine each axis in detail.

Chemical Pollution — VOCs and Formaldehyde

VOC (Volatile Organic Compounds) is a collective term for organic compounds that off-gas in vapor form at room temperature. Paints, adhesives, caulks, certain carpets, furniture, and cleaning products are the primary sources; reported health effects include eye, nose, and throat irritation, headaches, and central nervous system effects following chronic exposure.

HCHO (Formaldehyde) is the single chemical compound most frequently implicated among VOCs. Korea's Indoor Air Quality Control Act sets maintenance thresholds of 100 µg/m³ for multi-use facilities and 80 µg/m³ for facilities serving sensitive populations.

Carpet is often unfairly blamed, but in practice the greater source of emissions is frequently an uncertified combination of adhesive + cushion backing rather than the carpet pile itself. Because Green Label Plus certifies the three categories separately, all three must be individually verified for certification in the specification.

For domestic projects, KEITI (Korea Environment Industry & Technology Institute) eco-label certification is the primary benchmark; for global and LEED projects, Green Label Plus is cited alongside it. The two systems use different test methods and cannot substitute for each other.

Microorganisms — Mold Is Fundamentally a Moisture Problem

The WHO Dampness and Mould Guideline (2009) reports that 10–50% of indoor environments worldwide have dampness or mold problems. Mold will grow wherever food, moisture, and an appropriate temperature coexist simultaneously — in carpet, wallcovering, ceiling tiles, or HVAC ductwork.

The key is not killing the microorganisms themselves but blocking moisture. Mold spores are always present in the air, but they cannot germinate without water. The WHO states explicitly that "eliminating and minimizing persistent moisture is the most important means of mold control."

For carpet flooring, an open-cell cushion backing is the most effective first line of defense. It allows moisture rising from the subfloor to dissipate upward before it can condense, preventing the conditions in which mold can grow.

Closed-cell or conventional polyurethane cushion, by contrast, traps moisture and accelerates condensation. When reviewing specifications, it is advisable to verify the cushion structure (open-cell / closed-cell), breathability (perm value), and mold-resistance certification (ASTM G21, etc.) together.

Outdoor Particles — PM10 and PM2.5

Particulate matter is classified as PM10 (diameter ≤ 10 µm) and, within that, PM2.5 (diameter ≤ 2.5 µm). PM2.5 reaches deep into the alveoli and some fraction enters the bloodstream, making its health impact more significant.

Korea's Ministry of Environment sets maintenance standards in Annex 2 of the Enforcement Rules of the Indoor Air Quality Control Act: 100 µg/m³ for PM10 and 50 µg/m³ for PM2.5 in multi-use facilities. Facilities serving sensitive populations — daycare centers, postpartum care centers, medical institutions, and nursing homes — are subject to stricter limits of 75 and 35 respectively.

Simply closing windows on days with heavy particulate pollution is insufficient. While increasing building airtightness to reduce outdoor infiltration, it is also necessary to install sufficiently fine filters at the HVAC outdoor air intake and continuously recirculate and filter the indoor air.

Ventilation and Filtration — MERV 13 and ASHRAE 62.1

HVAC (Heating, Ventilation, Air Conditioning) serves two functions: bringing in sufficient outdoor air through ventilation, and removing particles and gases from incoming and recirculated air through filtration. Both have standardized quantitative benchmarks.

Ventilation rate requirements are calculated using the Ventilation Rate Procedure of ASHRAE 62.1 (Ventilation for Acceptable Indoor Air Quality). For office occupancies, the minimum outdoor air supply is 5 CFM per person plus 0.06 CFM/ft² of floor area.

Filters are rated using the MERV (Minimum Efficiency Reporting Value) scale per ASHRAE 52.2. The recommendation for residential and general commercial spaces is MERV 13 or above, which guarantees capture of ≥90% of PM10, ≥85% of PM2.5, and ≥50% of PM1.0.

Hospitals and laboratories use MERV 14–16 or HEPA.

As the MERV rating increases, filter pressure drop rises, increasing fan load and energy consumption. Rather than forcing a 1-inch filter to achieve MERV 13, it is common practice to switch to a 4–6-inch filter or to configure a two-stage filtration system (pre-MERV 8 + main MERV 13).

Carpet Cleaning — The CRI Seal of Approval Vacuum Rating

Carpet is commonly accused of being a reservoir for allergens, but more precisely, carpet acts as a temporary trap for dust and particles. Multiple studies show that with regular, thorough cleaning to prevent trapped particles from becoming airborne again, carpet can actually reduce PM exposure.

The objective standard for vacuum selection is the CRI Seal of Approval (SOA). It quantitatively evaluates three criteria — soil removal rate, dust containment, and carpet pile retention — using NASA's X-ray fluorescence measurement technology, assigning Bronze, Silver, or Gold ratings.

The Gold rating requires soil removal ≥55% and dust containment ≤35 µg/m³ — nearly twice as stringent as Silver (50–54% / ≤100) and Bronze (40–49% / ≤100). Many SOA-certified vacuums also incorporate HEPA filters to provide additional air quality benefits.

For in-house cleaning, a carpet-specific vacuum with an upright (rotating brush) motor and HEPA filter combination should be used; it should be noted that a standard cylinder vacuum is not effective at removing deep-pile particles. For detailed recommended specifications, it is advisable to consult both the carpet and vacuum manufacturers.

Priority Actions by Facility Type

Elevating all four axes simultaneously is ideal, but priorities vary by budget, timing, and facility characteristics. Identify the scenario below that most closely matches your situation and start with the first action listed for that case.

Frequently Asked Questions

Glossary

Abbreviations and standard numbers appearing in the text are compiled here for quick reference.

IAQ · Indoor Air Quality. The chemical, physical, and biological cleanliness of the air breathed indoors.

SBS · Sick Building Syndrome. A cluster of nonspecific symptoms occurring only while inside a particular building (WHO 1984).

BRI · Building-Related Illness. Unlike SBS, a case in which a specific diagnosis or pathogen is identified (e.g., Legionella).

VOC · HCHO · Volatile Organic Compounds / Formaldehyde. Chemical substances emitted by paints, adhesives, and finishing materials.

PM10 · PM2.5 · Particulate Matter with diameter ≤ 10 µm / ≤ 2.5 µm.

MERV · Minimum Efficiency Reporting Value. Filter efficiency rating per ASHRAE 52.2 (scale 1–16; higher = finer filtration).

HVAC · CFM · Heating Ventilation and Air Conditioning / Cubic Feet per Minute (unit of outdoor air supply rate).

References

Official URLs for the primary sources and standards cited in the text.

1. WHO Indoor Air Quality Guidelines — Dampness and Mould (2009): https://www.who.int/publications/i/item/9789289041683

2. Sick Building Syndrome definition (WHO 1984 reference): https://en.wikipedia.org/wiki/Sick_building_syndrome

3. CRI Green Label Plus (ASTM D5116 carpet, adhesive, and cushion VOC testing): https://carpet-rug.org/testing/green-label-plus/

4. CRI Seal of Approval vacuum ratings: https://carpet-rug.org/testing/seal-of-approval-program/vacuums/

5. Korea Indoor Air Quality Control Act Enforcement Rules [Annex 2] Maintenance Standards (Easy Law information): https://www.easylaw.go.kr/CSP/CnpClsMain.laf?csmSeq=1827&ccfNo=4&cciNo=1&cnpClsNo=2

6. ANSI/ASHRAE 62.1 Ventilation for Acceptable Indoor Air Quality: https://www.ashrae.org/technical-resources/bookstore/standards-62-1-62-2

7. EPA — What is a MERV rating (ASHRAE 52.2): https://www.epa.gov/indoor-air-quality-iaq/what-merv-rating

8. Hero image (Tim Witzdam · Unsplash License — commercial-free): https://unsplash.com/photos/a-plant-and-a-monitor-sit-on-a-white-table