Experimental and numerical study of the performance of upper-room ultraviolet germicidal irradiation with the effective Z-value of airborne bacteria

Figures & data

Figure 1. The configuration of the chamber. All dimensions are in m.

Figure 2. The eZ-value of S. marcescens (ATCC 6911). Each value is the average of three measured values and error bar represents the standard deviation.

Figure 3. The eZ-value of S. epidermidis (ATCC 12228). Each value for UR-UVGI off and on is the average of four and three measured values, respectively. Error bar represents the standard deviation.

Figure 4. The eZ-value of P. alcaligenes (ATCC 14909). Each value for UR-UVGI off and on is the average of two and three measured values, respectively. Error bar represents the standard deviation.

Figure 5. The eZ-value of M. luteus (ATCC 4698). Each value is the average of four measured values and error bar represents the standard deviation.

Table 1. The UV susceptibility constants (Z) of test bacteria reported in references Beggs et al. (2006), Kowalski (2009), Noakes et al. (2004a), and Yang et al. (2012).

Bacteria	Test media	Z (m^2/J)	UVGI	Reference
S. marcescens	Air	0.0983^a	Upper-room	Present study
		2.2619^b
		0.0043^c
	Air	0.089	Upper-room	Yang et al. (2012)
	Air	0.0433–0.0469	Upper-room	Beggs et al. (2006)
	Air	0.57	Single-pass	Ko et al. (2000)
	Air	0.35–0.45	Single-pass	Peccia et al. (2001)
	Air	1.83–2.45	Single-pass	Riley et al. (1976)
	Air	0.4449	Single-pass	Sharp (1940)
S. epidermidis	Air	0.0586^a	Upper-room	Present study
		1.3478^b
		0.0025^c
	Air	0.16210	Single-pass	VanOsdell and Foarde (2002)
	Air	0.11300	Single-pass	Nakamura (1987)
P. alcaligenes	Air	0.0476^a	Upper-room	Present study
		1.0949^b
		0.0021^c
M. luteus	Air	0.0115^a	Upper-room	Present study
		0.2645^b
		0.0005^c

^a Calculated by method: eZ=k_uv/I_rV, where k_uv is the equivalent air-exchange rate of bacteria inactivated by UR-UVGI, I_rV is the average irradiance of irradiated zone.

^b Calculated by Beggs et al.'s (2006) method: eZ = k_uv·h_r/(I_rV·h_i), where h_r is the height of room, h_i is the height of irradiated zone.

^c Calculated by Xu et al.'s (2003) method: eZ = k_uv·h_i/(I_rV·h_r).

Figure 6. Comparisons of the present simulation and the experiment of Yang et al. (2012) and the simulation of Yang et al. (2016). The inactivation rate (k_uv) of experiment is the difference of the slopes derived from “Ventilation” and “Ventilation + UR-UVGI.” Each point value is the average values of location A, B, and C at w = 2.05 m (Figures 5(d) and 6(d) in Yang et al. 2012). Error bar represents the standard deviation.

Figure 7. The average concentration of the tested bacteria in breathing zone (w ≤ 1.68 m) (C_b) with I_rV = 0.284 W/m² for different ACHs.

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