Sizing an air purifier correctly for your space is crucial for effective air cleaning. The primary method involves matching the purifier's capacity to the room size, often using the Clean Air Delivery Rate (CADR).
Understanding CADR and Room Size
Air purifiers are sized based on their ability to clean air in a given area. The key metric for this is typically the CADR, which indicates how quickly the air cleaner removes specific pollutants like smoke, dust, and pollen from a room. Higher CADR numbers mean faster cleaning.
To ensure an air purifier is effective for your room, it is important to select one specific for your room size. A widely recommended method is the "2/3 rule".
The 2/3 Rule for Sizing
According to this rule, you should find an air cleaner with a CADR that is at least 2/3 the square footage of the space. This ensures the purifier has enough power to adequately circulate and clean the air in the specified area.
Here's how to apply the rule:
- Measure your room's square footage: Multiply the length of the room by its width (in feet).
- Calculate the minimum required CADR: Multiply the square footage by 2/3 (or approximately 0.67).
Minimum Required CADR = Room Square Footage × (2/3)
Examples Using the 2/3 Rule
Let's look at a few examples:
- Small Bedroom (10 ft x 12 ft):
- Square Footage: 10 * 12 = 120 sq ft
- Minimum CADR: 120 * (2/3) ≈ 80 CADR
- Medium Living Room (15 ft x 20 ft):
- Square Footage: 15 * 20 = 300 sq ft
- Minimum CADR: 300 * (2/3) = 200 CADR
- Large Open Area (20 ft x 30 ft):
- Square Footage: 20 * 30 = 600 sq ft
- Minimum CADR: 600 * (2/3) = 400 CADR
It's generally better to choose an air purifier with a higher CADR than the minimum required, especially if you have allergies, pets, or significant air quality concerns.
Quick Reference Table (Examples)
| Room Size (Sq Ft) | Minimum Recommended CADR (2/3 Rule) |
|---|---|
| 100 | 67 |
| 200 | 133 |
| 300 | 200 |
| 400 | 267 |
| 500 | 333 |
| 600 | 400 |
Note: CADR values are typically rounded to the nearest 5 or 10.
Other Factors to Consider
While the 2/3 rule based on CADR and square footage is a primary guideline, other factors influence the best size for your needs:
- Air Changes Per Hour (ACH): Some manufacturers also list the number of times the air purifier can exchange the air in a standard height room (usually 8 feet) per hour. For general use, 2-3 ACH is common. For allergy or asthma sufferers, 4-5+ ACH is often recommended, which would require a higher CADR for the same room size.
- Type of Pollutants: CADR is often given for smoke, dust, and pollen. If you are primarily concerned about VOCs (Volatile Organic Compounds) or odors, look for models with adequate activated carbon filters and ensure the overall CADR is sufficient for the room size to move air effectively through these filters.
- Placement: The air purifier should be placed where air can circulate freely, away from walls and furniture, which can impact its effective coverage.
- Personal Sensitivity: Individuals with severe allergies or respiratory issues may benefit from oversizing the air purifier (choosing one with a significantly higher CADR than the minimum) to achieve more frequent air changes.
By considering your room size, the CADR rating, and these additional factors, you can select an air purifier that is appropriately sized to provide clean air for your specific needs.
