A detailed study published in Heliyon provides one of the most thorough analyses of how effectively HEPA air purifiers remove different sizes of indoor pollutants. The research, conducted in India, tested two different air purifiers under real-world conditions and revealed important insights about which particles are easiest to remove and when air purifiers work best.

The study fills a critical gap in air purifier research by examining not just overall particle reduction, but how effectively different sized particles are captured. This matters because smaller particles pose the greatest health risks, penetrating deep into lungs and even entering the bloodstream.

Key Findings: Size Matters for Air Purifier Effectiveness

The research tested particle removal across six different size categories, from ultrafine 0.25-micron particles up to larger 10-micron particles. Results varied dramatically based on particle size and environmental conditions.

General Indoor Air Results:

• Air Purifier I: 12-52% reduction across different particle sizes
• Air Purifier II: 37-73% reduction across different particle sizes

External Source Conditions (candles and incense):

• Air Purifier I: 29-53% reduction
• Air Purifier II: 52-68% reduction

Both air purifiers performed significantly better when dealing with external pollution sources compared to general indoor air. This suggests HEPA filtration becomes more effective when particle concentrations are elevated.

The study found that larger particles were generally easier to remove than smaller ones, though this pattern varied between different air purifier models and operating conditions.

Why Air Purifiers Work Better During High-Pollution Events

The research revealed a counterintuitive finding: air purifiers were more effective when dealing with candle and incense smoke than during normal indoor conditions. This occurs because higher particle concentrations provide more opportunities for the filtration mechanisms to capture pollutants.

HEPA filters work through four main mechanisms: interception, inertial impaction, diffusion, and sieving. During high-pollution events, these mechanisms become more efficient as particles have more interactions with filter fibers.

The study used candles and incense as pollution sources because they're commonly used in homes and generate significant amounts of fine particles. Candle burning can produce PM2.5 concentrations of 1,200 μg/m³—far exceeding healthy indoor air quality standards.

Professional-grade air purification systems like the Air Oasis iAdaptAir address these challenges through multi-stage filtration that combines HEPA technology with UV-C sterilization and ionization for comprehensive particle removal.

The Critical Importance of Clean Air Delivery Rate (CADR)

The study compared two air purifiers with different Clean Air Delivery Rates (CADR)—120 m³/h versus 150 m³/h. The higher CADR unit consistently performed better, confirming that airflow capacity directly impacts filtration effectiveness.

CADR measures the volume of filtered air delivered by an air purifier. Higher CADR ratings indicate more air processed per hour, leading to faster room air turnover and more effective pollutant removal.

The research showed that the air purifier with higher CADR and larger coverage area (35 m² vs 19 m²) removed particles more effectively across all size ranges. This supports choosing air purifiers with specifications matched to room size and intended use.

Health Risk Reduction: Quantified Benefits

Beyond particle removal percentages, the study quantified actual health risk reduction from air purifier use. Results showed significant decreases in both cancer risk and non-cancer health hazards.

Health Quotient (HQ) Reductions:

• Air Purifier I reduced health risks by 2.07 times in normal conditions
• Air Purifier II reduced health risks by 2.16 times in normal conditions
• During candle/incense events, risk reductions reached 2.94 times

The study calculated these reductions using established EPA risk assessment methods, providing objective evidence that air purifiers deliver measurable health protection rather than just comfort improvements.

For children, who face higher risks from particle exposure, the health benefits were even more pronounced. This supports using professional air purification in homes with vulnerable family members.

Surprising Findings About Ion Generation

The research revealed an unexpected issue with some air purifiers: they can actually increase certain ion concentrations while reducing particles. Some models released ions continuously as part of their purification process, leading to elevated indoor ion levels even after air was cleaned.

The study found that mechanical HEPA filtration alone provided more predictable results than systems combining filtration with ion generation. The authors recommend choosing air purifiers with mechanical filters rather than those relying primarily on ion generation for purification.

This finding highlights the importance of understanding air purifier technology rather than assuming all purification methods are equivalent. The Air Oasis systems use proven HEPA filtration as their primary mechanism while incorporating controlled ionization that doesn't create unpredictable ion concentrations.

Limitations Even High-Performance Air Purifiers Face

Despite impressive particle reduction percentages, the study found that even after air purification, particle concentrations often remained above WHO air quality guidelines. This occurred particularly during high-pollution events like candle and incense burning.

The research confirmed that source control—preventing pollution generation—remains more effective than air purification alone. However, when source elimination isn't possible, professional air purification provides significant protection.

The study's authors noted that short-term testing may not capture long-term performance variations, and seasonal differences could affect results. Additional research examining air purifier effectiveness across different climates and longer time periods would strengthen these findings.

Practical Implications for Choosing Air Purifiers

The research provides clear guidance for selecting effective air purification systems:

Choose Higher CADR Ratings: Air purifiers with higher CADR performed better across all conditions and particle sizes.

Prioritize HEPA Filtration: Mechanical HEPA filters provided more predictable and effective particle removal than ion-based systems.

Size Appropriately: Match air purifier capacity to room size for optimal performance.

Expect Better Performance During Pollution Events: Air purifiers work more effectively when particle concentrations are elevated.

The Future of Indoor Air Quality Research

This study represents important progress in understanding real-world air purifier performance. Future research should examine effectiveness across different seasons, longer time periods, and various indoor environments.

The authors suggest investigating air purifier performance against other pollutants beyond particles, including volatile organic compounds and biological contaminants. Understanding how different technologies work together could improve comprehensive air quality management.

As air quality concerns grow globally, research like this provides the scientific foundation for making informed decisions about indoor air protection strategies.

Evidence-Based Air Quality Protection

This comprehensive research confirms that HEPA air purifiers provide measurable health protection through significant particle reduction, with effectiveness varying by particle size, environmental conditions, and air purifier specifications.

The study's findings support investing in professional-grade air purification systems with appropriate CADR ratings and proven HEPA technology rather than relying on less-tested purification methods.

Ready to implement research-proven air quality protection in your home? Shop Air Oasis today for HEPA air purification systems designed with the specifications and technology validated by scientific research.