Inactivation of Airborne Microorganisms Using Novel Ultraviolet Radiation Sources in Reflective Flow-Through Control Devices

Figures & data

FIG. 1 Schematic of the experimental test system used to evaluate the bench-scale flow-through UVGI control devices.

FIG. 2 Illustration (not to scale) of the 2-D axisymetric (along dashed line) model geometry for the flow-through control devices with (a) mercury and xenon lamps and (b) LEDs.

FIG. 3 Particle size distributions of mass concentration for (a) B. subtilis and (b) M. parafortuitum bioaerosol.

FIG. 4 Surviving fraction versus fluence for B. subtilis at 50% relative humidity. Error bars represent one standard deviation of the mean (n = 16).

FIG. 5 Surviving fraction versus fluence for B. subtilis at 15% relative humidity. Error bars represent one standard deviation of the mean (n = 14).

FIG. 6 Surviving fraction versus fluence for M. parafortuitum at 15% relative humidity. Error bars represent one standard deviation of the mean (n = 9).

TABLE 1 Experimental scenarios and comparison between control device effectiveness measured experimentally (average +/− SD) and modeled for UV inactivation of airborne B. subtilis and M. parafortuitum

						Effectiveness
Microorganism	RH	Lamp	Coated	Airflow	Number of experiments	Experimental			Model*	Error**
(Type)	(%)	(Type)	(Yes/No)	(L/s)	(#)	(%)			(%)	(%)
B. subtilis	50	Mercury	Yes	4	2	65.1	+/−	2.7	64.6	–0.5
				2	2	87.8	+/−	1.4	87.8	–0.1
			No	2	2	63.4	+/−	4.4	68.7	5.3
				1	2	93.1	+/−	0.7	91.6	–1.5
		LED	Yes	0.32	2	41.4	+/−	8.3	50.9	9.4
				0.2	2	72.1	+/−	1.8	67.9	–4.2
		Xenon	Yes	4	2	75.1	+/−	3.3	67.5	–7.6
			No	2	2	78.7	+/−	2.7	72.0	–6.7
	15	Mercury	Yes	4	2	82.7	+/−	1.6	72.5	–10.2
				2	2	96.9	+/−	0.7	92.7	–4.2
			No	2	2	73.1	+/−	2.8	76.4	3.3
				1	2	90.4	+/−	1.2	95.4	5.0
		Xenon	Yes	4	2	90.5	+/−	1.0	75.3	–15.2
			No	4	2	40.4	+/−	5.0	53.7	13.3
				2	2	81.0	+/−	4.3	79.5	–1.5
M. parafortuitum		Mercury	Yes	4	2	97.3	+/−	0.4	93.6	–3.8
			No	4	3	83.6	+/−	2.5	74.4	–9.1
		Xenon	Yes	4	2	96.6	+/−	0.8	94.9	–1.7
			No	4	2	77.8	+/−	2.8	80.5	2.7

FIG. 7 The UV-C fluence rate for LED control device with coated tube walls as measured by actinometry and predicted by the photon trace model.

FIG. 8 The UV-C fluence rate for mercury lamp control device with (a) uncoated and (b) coated tube walls as measured by actinometry and predicted by the photon trace model.

FIG. 9 The UV-C fluence rate for xenon lamp control device with (a) uncoated and (b) coated tube walls as measured by actinometry and predicted by the photon trace model.