When it comes to clean air, guessing is not an option. Buying an air purifier that is too small for your room is a common mistake that leads to poor air quality, wasted electricity, and shortened filter life. To effectively remove mold spores, dust, and volatile organic compounds (VOCs), you need a unit specifically sized for your space's volume and air-cleaning needs.
Whether you are managing a small bedroom or a damp 2,000 sq. ft. crawlspace, this guide will show you how to calculate the perfect fit using CADR, ACH, and CFM.
The Critical Metrics: CADR vs. ACH
To determine "what size air purifier do I need," you must look past the marketing "room size" claims on the box and focus on two scientific ratings:
Clean Air Delivery Rate (CADR)
CADR is a metric developed by AHAM that measures how much clean air a purifier delivers per minute. It is typically broken down into three categories: Smoke, Dust, and Pollen.
- The Rule of Thumb: Your unit's smoke CADR should be at least 2/3 of the room’s square footage.
- Example: A 300 sq. ft. room needs a CADR of at least 200.
Air Changes Per Hour (ACH)
ACH indicates how many times the purifier can refresh the entire volume of air in a room every 60 minutes.
- Healthy Standard: 4 to 5 ACH (refreshes air every 12–15 minutes).
- Medical/Allergy Grade: 6+ ACH.
- Restoration/Crawlspace: Professionals often aim for 6 ACH to manage high mold or dust loads.
2. Calculation Guide: How to Size Your Space
Don't rely on floor area alone. Ceiling height matters because air purifiers clean volume, not just square feet.
The Volume Formula:
To find the required CFM (Cubic Feet per Minute) for your room:
- Calculate Volume: $Length \times Width \times Height = Volume (ft^3)$
- Determine Desired ACH: (Use 5 for high-performance cleaning).
- Calculate CFM: $\frac{Volume \times ACH}{60} = Required CFM$
Sizing Reference Table for AlorAir Units
|
Room Type |
Square Footage |
Volume (8ft Ceiling) |
Recommended CADR/CFM |
Best AlorAir Model |
|
Small Bedroom |
250 sq. ft. |
2,000 $ft^3$ |
160 – 200 |
PureAiro HEPA Max 870 |
|
Living Area |
500 sq. ft. |
4,000 $ft^3$ |
350 – 450 |
PureAiro HEPA 770 |
|
Lg. Basement |
1,000 sq. ft. |
8,000 $ft^3$ |
550+ |
CleanShield HEPA 550 |
|
Industrial Site |
2,000+ sq. ft. |
16,000 $ft^3$ |
1,000+ |
HEPA 550 (Daisy-Chained) |
Why Professional "Air Scrubbers" Beat Home Purifiers
In crawlspaces or restoration projects, a standard home air purifier is often underpowered. AlorAir Air Scrubbers are designed for high-pressure airflow and specialized filtration.
- Ducting Capability: Unlike home units, AlorAir scrubbers can be ducted to create negative air pressure, preventing mold spores from leaking into other parts of the house.
- Rugged Durability: Built with rotomolded plastic or stainless steel, these units survive the humidity of a crawlspace where retail units would rust or short-circuit.
- Stackability: For huge spaces (over 3,000 sq. ft.), professional units can be stacked to increase CADR without taking up excessive floor space.
Oversizing: The Secret to Quiet Performance
A common question is: "Can an air purifier be too big?" The answer is no. Using a larger unit like the AlorAir PureAiro HEPA Max 870 in a smaller room allows you to run the fan on a lower speed. This results in:
- Less Noise: Quiet operation while still meeting your ACH goals.
- Longer Filter Life: Less strain on the motor and more surface area to trap particles.
- Lower Power Bills: Running a large motor at low speed is often more efficient than a small motor at "Turbo" speed.
Specialized Filtration Needs
The "size" of the purifier isn't just about the fan; it's about the filter depth.
- For Mold/Allergens: You need a True HEPA filter. Ensure your unit is sized to maintain high airflow even as the filter fills up.
- For Smoke/Odors: You need a unit with a significant Activated Carbon load. Small home units only have a thin carbon sheet; AlorAir units use thick carbon pellets to "soak up" smells at the molecular level.
Industrial Scaling: The Power of Daisy-Chaining
For large-scale restoration or massive crawlspaces, a single air purifier might not reach every corner. This is where professional units like the AlorAir CleanShield HEPA 550 shine. They feature an integrated GFCI Duplex Outlet, allowing for a process called "Daisy-Chaining."
- Simplified Power Management: You can connect up to three units to a single wall outlet. This eliminates the need for dangerous extension cords snaking through a damp crawlspace.
- Redundant Filtration: By placing units at opposite ends of a long crawlspace, you ensure that "dead air" zones are eliminated, maintaining a consistent ACH (Air Changes Per Hour) across the entire foundation.
- Flexible Negative Pressure: Daisy-chained units can be ducted together to create a high-volume vacuum, ensuring that no dust or mold spores escape into the living quarters during a major remediation project.
Cost Analysis: Is Running a Purifier Expensive?
A common barrier for homeowners is the fear of a skyrocketing electric bill. However, modern AlorAir units are engineered for high-efficiency, continuous use.
Estimated Monthly Operating Costs (Based on $0.17/kWh)
|
Model |
Avg. Wattage (Med Speed) |
Daily Cost (24/7) |
Monthly Cost |
|
PureAiro HEPA Max 870 |
120W |
$0.49 |
$14.70 |
|
CleanShield HEPA 550 |
150W |
$0.61 |
$18.30 |
|
Standard Retail Tower |
80W |
$0.32 |
$9.60 |
The Professional Advantage: While an AlorAir unit uses more power than a small retail tower, it cleans 3-4 times the air volume. You would need four retail units to match the cleaning power of one CleanShield HEPA 550, making the professional unit significantly cheaper to operate per cubic foot of clean air.
Professional Maintenance: Protecting Your Investment
To maintain the "size" of your airflow (CFM), you must protect the motor from resistance caused by clogged filters.
- The "Pre-Filter" Defense: AlorAir units use a secondary pre-filter to catch "the big stuff" (pet hair, sawdust). Checking this weekly can extend the life of your expensive HEPA filter by 300%.
- Pressure Indicator Lights: Unlike home units that use simple timers, AlorAir units often feature an onboard pressure gauge or indicator light. This tells you exactly when the filter is too dirty to allow proper airflow, ensuring you never run an inefficient machine.
- Cleaning the Housing: In crawlspaces, the exterior of your unit will get muddy. Periodically wiping down the rotomolded housing and ensuring the intake grilles are clear will prevent the motor from overheating.
Frequently Asked Questions
How do I know if my air purifier is working?
You can use a laser particle counter to check the air coming out of the exhaust. For a more tactile check, the air in the room should smell "neutral" (no musty or dusty odors) within 30 minutes of running the unit on its calculated setting.
Is it better to have one large unit or two small ones?
For open-concept spaces, one large unit is often more efficient. However, if your home has many walls and doorways, two smaller units (one in each room) will provide better air distribution than one large unit trying to pull air through a hallway.
Does ceiling height really matter for air purifiers?
Absolutely. A room with 12-foot ceilings has 50% more air than a room with 8-foot ceilings. If you have vaulted ceilings, you must use the Volume Formula mentioned above to avoid undersizing your unit.
What is the difference between CFM and CADR?
CFM (Cubic Feet per Minute) is the raw power of the fan. CADR (Clean Air Delivery Rate) is the amount of filtered air. A unit with high CFM but a poor filter will have a low CADR. Always look for the CADR rating for the most accurate sizing.
Can I use an AlorAir air scrubber in my living room?
Yes. While they are designed for industrial use, their high CADR makes them excellent for homes with severe mold issues, heavy smoking, or pet dander. Many users prefer them for their durability and superior carbon filtration.
Do I need to run my air purifier 24/7?
For the best results, yes. Modern units like the AlorAir Sentinel and PureAiro series are designed for continuous operation and have low power consumption on their medium/low settings.
Conclusion
Knowing "what size air purifier do I need" is the first step toward a healthier home. By calculating your room volume and targeting a minimum of 5 Air Changes Per Hour, you ensure that mold, dust, and allergens are removed faster than they can accumulate.
