Performance of wearable ionization air cleaners: Ozone emission and particle removal

Figures & data

Table 1. Characteristics of the four selected wearable air cleaners.

Air Cleaner	Marketing/manufacturer description	Description	Dimensions (cm)	Weight (g)	Battery	Retail price (USD)
AC1	Electronic propulsion directs cleaner air toward mouth and nose	Electron kinetic transducer produces airflows with negative ion generated by corona discharge with metallic cathodes. No fan and no particle filter.	11.4 × 8.4 × 3.8	86	Four AA Batteries	49.99
AC2	Mate personal ionic air purifier: Emits ions and 0.028 ppm ozone. Target: virus, bacteria, odors, chemical contaminants and dust	Negative ions generated by corona discharge with metallic cathodes. Positively charged metal grid removes the particles carrying negative charges. No fan and no particle filter.	6.4 × 3.8 × 2.0	81	One CR123A Battery	80.75
AC3	Neck air purifier: Emits negative ions. Target: odors, virus, particles	High voltage corona discharge with metallic cathodes generates negative ions. No fan and no particle filter.	6.1 × 3.8 × 3.3	54	Built-in Rechargeable Battery	27.78
AC4	Travel air purifier: Emits constant steam of negative ions. Target: viruses, bacteria, pollen, dust, etc.	Negative ions generated by corona discharge with carbon fiber cathodes. Positively charged metal ring attracts the particles carrying negative charges. No fan and no particle filter.	7.6 × 3.3 × 2.8	50	Two CR2025 Batteries	79.99

Figure 1. Schematic diagram of the test chamber.

Figure 2. Ozone concentration in the chamber with a wearable ionization air cleaner operating.

Figure 3. Ozone emission rates of tested wearable ionization air cleaners.

Figure 4. Removal rates of total particles in the measured size range and time-averaged ozone emission rates of wearable air cleaners.

Table 2. Comparison of CADR and ozone emission rate between the selected wearable ionization air cleaner in this study and other air cleaners from references.

Air Cleaner		CADR for size-resolved number concentration of ultrafine particles (m^3·h^−1)	CADR for mass concentration of fine particles (m^3·h^−1)	Ozone emission rate (mg·h^−1)
Wearable	AC1	/	/	0.669
	AC2	/	/	0.034
	AC3	1.09–5.20	0.70	0.00
	AC4	2.24–19.7	2.47	0.00
	Phillips et al. 1999	/	/	0.102 – 0.114
	Britigan et al. 2006	/	/	0.3–0.5
Household	Chan and Cheng 2006	/	53.58	/
	Mølgaard et al. 2014	46–119	/	/
	Zuraimi et al. 2011	5–45	/	/
	Waring et al. 2008	16–76	/	3.3±0.2
		17–74	/	4.3±0.2
	Niu et al. 2001	/	/	0.065–2.76
	Britigan et al. 2006	/	/	0.16–220

Figure 5. Size-resolved particle removal rates of fully charged wearable air cleaners.

Figure 6. Mass removal rates of PM_2.5 by fully charged wearable air cleaner.

Table 3. Total particle number removal rate and voltage by AC1 and AC4 of different battery conditions.

		Elapsed Time
Air Cleaner	Measured Parameters	0 h	12 h	24 h	36 h	48 h	72 h
AC1	Total particle removal rate (h^−1)	3.76	3.33	3.38	3.14	NA	NA
	Voltage (V)	1.93	1.74	1.71	1.59	NA	NA
AC4	Total particle removal rate (h^−1)	15.30	14.20	18.10	10.80	6.19	6.22
	Voltage (V)	4.35	3.97	3.92	3.94	3.66	3.49

Data are not available for AC1 at 48 h and 72 h because the battery voltage level became insufficient to operate the device after 36 h.

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