Fresh Air In
Learning Objectives
Students will be able to:
- Explain why fresh air is important for indoor air quality
- Describe how ventilation works
- Understand what "air changes per hour" means
- Identify ways to improve ventilation in a room
"Why does bringing in outside air help keep us healthy?"
There are TWO main ways to clean indoor air:
Filtration
Takes dirty air, removes particles, returns clean air
- Air stays inside
- Just removes particles
- Doesn't remove CO2 or add oxygen
- Good for particles and some germs
Ventilation
Replaces indoor air with fresh outdoor air
- Brings in fresh air
- Removes everything - particles, CO2, germs, odors
- Adds fresh oxygen
- Like opening windows!
Best Strategy: Both!
For the healthiest air, use BOTH filtration AND ventilation together. Filters catch particles, ventilation brings in fresh air and removes germs!
Ventilation is about exchanging indoor air for outdoor air:
Natural Ventilation
Open windows and doors! Wind and temperature differences move air.
Mechanical Ventilation
HVAC systems and exhaust fans that move air with motors.
Mixed Ventilation
Both together! Open windows PLUS fans to move more air.
What is ACH?
Air Changes Per Hour (ACH) tells us how many times ALL the air in a room gets replaced with fresh air in one hour.
| ACH | What It Means | Example |
|---|---|---|
| 1 ACH | All air replaced once per hour | Poorly ventilated room |
| 3 ACH | All air replaced 3 times per hour | Typical office |
| 6+ ACH | All air replaced 6+ times per hour | Good classroom ventilation! |
| 12+ ACH | All air replaced every 5 minutes | Hospital rooms |
Ribbon Test for Ventilation
Materials: Tissue paper strips or ribbon, tape
- Tape tissue paper strips near windows, doors, and air vents
- Observe: Are the strips moving? How much?
- Try opening/closing windows - what happens?
- Check near HVAC vents - is air coming out?
- Record your observations!
Observation Table
| Location | Windows Closed | Windows Open |
|---|---|---|
| Near window | ||
| Near door | ||
| Near vent | ||
| Middle of room |
Rate: Still / Slight Movement / Moving / Strong Movement
Free or Low Cost
- Open windows (even a crack helps!)
- Open doors to hallways
- Use box fans in windows
- Create cross-ventilation (windows on opposite sides)
- Run bathroom exhaust fans
Building Changes
- Upgrade HVAC system
- Add more air intake
- Install exhaust fans
- Add ERV/HRV systems
- Improve air distribution
Think of it like this: If someone adds a drop of food coloring to a small glass of water, it turns dark. But if you add a drop to a swimming pool, you can't even see it!
Ventilation works the same way with germs and pollution:
- In a room with poor ventilation, germs and CO2 build up
- With good ventilation, fresh air constantly dilutes them
- More fresh air = lower concentration of bad stuff!
Record and answer:
- What is the difference between filtration and ventilation?
- What does "6 ACH" mean?
- Where in our classroom did you observe the most air movement?
- List 3 ways to improve ventilation in a room
- Why is the "dilution solution" important for reducing germs?
Key Takeaways
- Ventilation brings fresh outdoor air in and pushes stale air out
- ACH (Air Changes per Hour) measures how well a room is ventilated
- Higher ACH = more fresh air = healthier indoor environment
- Opening windows is a simple, free way to improve ventilation
- Using BOTH filtration AND ventilation gives the best results!
Ventilation
The process of bringing fresh outdoor air into a space and removing stale indoor air.
ACH (Air Changes per Hour)
How many times all the air in a room is replaced with fresh air in one hour.
Cross-ventilation
Having openings on opposite sides of a room to let air flow through.
Dilution
Making something weaker by adding more of something else (like adding fresh air).