Chapter 7: Indoor Air Quality (IAQ) & Ventilation
🔹 7.1 What is Indoor Air Quality (IAQ)?
Indoor Air Quality (IAQ) refers to the cleanliness, freshness, and healthiness of the air inside buildings.
Good IAQ ensures:
Comfort
Productivity
Health (especially in hospitals, schools, homes)
Poor IAQ can cause:
Headaches, allergies, eye irritation
Breathing problems (asthma, coughing)
Sick Building Syndrome (SBS)
🔹 7.2 Common Indoor Air Pollutants
| Pollutant | Source |
|---|---|
| Carbon dioxide (CO₂) | Human respiration |
| Particulate matter (PM) | Dust, smoke, printers |
| VOCs (Volatile Organic Compounds) | Paint, cleaning agents |
| Biologicals | Mold, bacteria, pollen |
| Formaldehyde | Furniture, insulation |
| Radon | Soil under buildings |
🔹 7.3 What is Ventilation?
Ventilation is the process of bringing fresh outdoor air into a building and removing stale indoor air.
There are two main types:
Natural Ventilation: Through windows, vents, wind
Mechanical Ventilation: Using fans, ducts, exhausts
🔹 7.4 Types of Mechanical Ventilation
| Type | Description |
|---|---|
| Exhaust Ventilation | Removes indoor air (e.g., kitchen, bathrooms) |
| Supply Ventilation | Brings in fresh air under pressure |
| Balanced Ventilation | Combines both supply and exhaust |
| Energy Recovery Ventilator (ERV) | Transfers heat & moisture between outgoing & incoming air |
| Heat Recovery Ventilator (HRV) | Transfers only heat (not moisture) |
🔹 7.5 IAQ Standards & Guidelines
| Organization | Standard/Guideline |
|---|---|
| ASHRAE 62.1 | Acceptable Indoor Air Quality in buildings |
| WHO | Limits for indoor air pollutants |
| ISHRAE | Indian standards for ventilation rates |
ASHRAE Recommended Ventilation Rate:
Office: 15–20 CFM/person
Classroom: 10–15 CFM/person
Hospital room: 25–30 CFM/person
🔹 7.6 IAQ Control Methods
| Method | Application |
|---|---|
| Air Filtration | HEPA filters for dust, bacteria |
| UVGI (UV Germicidal) | Destroys microorganisms in ducts |
| Activated Carbon | Removes VOCs and odors |
| Humidity Control | Dehumidifiers or humidifiers |
| Fresh Air Ducting | Brings in filtered outdoor air |
🔹 7.7 IAQ in Special Spaces
| Space | Special Requirement |
|---|---|
| Hospitals | HEPA filtration, negative pressure isolation |
| Laboratories | Exhaust hoods, fume extraction |
| Clean Rooms | Laminar flow, 99.99% filtration |
| Data Centers | Temperature + humidity + particle control |
🛠️ Practical Tips for Improving IAQ
Regularly clean HVAC filters
Install exhaust fans in kitchens & bathrooms
Use indoor plants (natural air purifiers)
Avoid heavy use of aerosol sprays or incense
Ensure good duct sealing to avoid leakage
🧪 Simple IAQ Tools
CO₂ Monitor: Checks ventilation adequacy
PM2.5 Sensor: Measures fine dust particles
VOC Sensor: Detects harmful gases in air
📄 Assignment Questions
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What is Indoor Air Quality and why is it important in HVAC?
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Name five indoor air pollutants and their sources.
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Explain the difference between natural and mechanical ventilation.
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What are ERVs and HRVs? How do they work?
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List five methods used to improve IAQ.
💼 Interview Questions
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What is Sick Building Syndrome?
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How can you improve IAQ in a hospital?
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What are the ASHRAE standards for ventilation?
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What is the difference between HEPA and carbon filters?
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How does relative humidity affect IAQ?