Experimental Study on Optimal Clean Air Delivery Rate Filter Thickness of Indoor Air Purifiers

Abstract

Abstract This study investigates the relationship between filter thickness and air purifiers’ Clean Air Delivery Rate (CADR). Despite theoretical analysis of optimal CADR filter thickness, experimental validation has been lacking. This research addresses this gap by testing four filter brands and four fan powers to determine the optimal configuration for maximum CADR. A homemade air purifier with varying filter thicknesses and fan powers was utilized. Filtration efficiency was assessed by measuring particulate matter upstream and downstream of the air purifier using a Scanning Mobility Particle Sizer (SMPS). CADR was calculated via the single-pass method. Results indicate that filtration efficiency increases with thicker filters; however, the optimal CADR is achieved at a specific filter thickness. For instance, with a fan power of 2.7 W, optimal CADR corresponded to 15–55% filtration efficiency for 100 nm particles and 10–36% for Most Penetrating Particle Size (MPPS) particles (240–420 nm). When the same filter brand (Filter M) was used with varying fan powers (2.7–23.4 W), the highest CADR occurred consistently at around 35% filtration efficiency, irrespective of fan power, with MPPS ranging from 200–320 nm. The study concludes that for each fan and filter combination, an optimal filter thickness exists to maximize CADR, which is crucial for enhancing air purifier efficiency and longevity. The findings recommend slightly reducing filter thickness below the optimal CADR thickness to prolong filter life while maintaining effectiveness. This study provides practical insights for improving the design and performance of air purifiers used in indoor environments.

Keywords

• Air purifier
• Filter quality factor
• Fan performance curve
• Clean air delivery rate
• Filter thickness