Air Purifier and Fresh Air Ventilation Cooling Solutions -- DC Fans | Herays
Application Solution

Air Purifier and Fresh Air Ventilation

Airflow support for filtration, fresh air exchange, and compact ventilation

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Problem Space

Industry Challenges

Understanding the specific thermal and environmental demands of Air Purifier and Fresh Air Ventilation environments is the foundation of every Herays solution.

Air purifiers, HEPA filtration systems, and residential fresh air ventilation units must move substantial volumes of air continuously through dense filter media while producing noise levels acceptable in bedrooms, nurseries, and living spaces — and they must do this for 8,760 hours per year, year after year, with no maintenance between filter changes. The fan in an air purifier is not cooling a component; it is the core functional element of the product. Its performance, noise, and reliability directly determine whether the product delivers on its health claims and whether the customer returns it.

  • HEPA filter static pressure overcome requires centrifugal or high-static axial fans — a H13 HEPA filter at rated airflow imposes 100–300 Pa of static pressure. Standard low-cost axial fans operating against this restriction deliver far less than their open-frame CFM rating. The fan must be selected against the system pressure-flow curve at filter replacement (clean filter) and end-of-life (loaded filter) conditions.
  • Ultra-quiet for bedroom and nursery use — leading air purifiers achieve 20–24 dBA at their lowest fan speed setting. Even “high” speed settings must be below 50 dBA for the product to be usable in a bedroom environment. Acoustic performance is the primary purchase driver and return trigger for air purifier consumers.
  • PWM speed control with multiple speed steps or continuous variation — air purifiers offer at minimum two or three speed settings; premium models offer continuous fan speed variation driven by PM2.5 sensor feedback. The fan must respond smoothly and repeatably to speed commands across its full operating range.
  • Long filter-change-interval reliability — filter replacement intervals of 6–12 months mean the fan runs 4,000–8,000 hours between filter changes. Ball bearings are mandatory; sleeve-bearing fans that meet this runtime without noise increase are uncommon.
  • 12V or 24V DC for battery-backup and portable applications — residential air purifiers are primarily AC-powered, but portable air purifiers for travel, car use, and battery-backup installations use 12V DC fans powered from battery packs or USB power banks with boost converters.

Herays DC axial fans and centrifugal blowers are used in residential and commercial air purifiers and fresh air ventilation systems, available in configurations suited to both filter-box (axial fan) and duct (centrifugal blower) air handling designs.

  • HR1225 12V — 120×120×25 mm, 134 CFM at open frame, ball bearing. For compact air purifier filter boxes where the fan sits directly in front of the HEPA stage. Ball-bearing construction provides low rumble noise at minimum speed critical for bedroom-mode operation.
  • HR1238 12V (−SF) — 120×120×38 mm, 186 CFM, 13.9 mmH₂O static pressure. The additional static pressure of the 38 mm frame provides meaningful CADR improvement through H13 HEPA filters with significant end-of-life loading compared to thinner 25 mm fans.

For larger room-size air purifiers and fresh air ventilation units requiring higher CADR (above 300 m³/h), centrifugal blowers with radial impellers are available from Herays — contact for specifications.

How do I calculate the CADR (Clean Air Delivery Rate) my air purifier fan achieves through a HEPA filter? Measure the actual airflow through your filter at its installed back-pressure using a calibrated anemometer or flow hood at the outlet. Multiply by filter capture efficiency (H13 HEPA = 99.95% at 0.3 µm) to get effective clean air delivery rate. Fan open-frame CFM ratings are not useful for CADR calculation — always measure through the filter in the actual enclosure.

Why does air purifier noise increase over the filter’s life? As the filter loads with particulates, its flow restriction increases. To maintain airflow (and CADR), the controller increases fan speed — which directly increases noise. Well-designed air purifiers incorporate PM2.5 feedback that varies both speed and noise throughout the filter life. Users who notice increasing noise over time should check filter replacement schedule first before assuming fan degradation.

What is the optimal fan position in an air purifier — before the filter (pulling) or after the filter (pushing)? Pulling air through the filter (fan after filter) keeps the fan motor in clean filtered air, prevents contamination of the motor, and reduces fan corrosion from corrosive particles captured by the filter. This is the standard design for HEPA air purifiers. Pushing (fan before filter) is sometimes used in ventilation units where the fan handles unfiltered air and the filter is downstream — this is acceptable but requires the fan to be specified for contaminated airstreams.

Contact Herays for air purifier and ventilation fan specifications, CADR test data, and OEM supply programs for air quality product manufacturers.

Herays Approach

Our Solution

Precision-engineered DC fan technologies tailored to the performance and reliability requirements of Air Purifier and Fresh Air Ventilation applications.

Why Herays

Key Features for Air Purifier and Fresh Air Ventilation

Filter airflow

Air movement options for HEPA, carbon, and compact filter paths.

Indoor low noise

Fan selections for user-facing indoor ventilation equipment.

Compact ventilation

Axial fan and blower choices for small fresh air modules.

Application Engineering

Ready to find the right cooling solution for Air Purifier and Fresh Air Ventilation?

Our application engineers are available to help you select the right product for your system requirements.

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