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. 2019 Nov 7;14(11):e0225047. doi: 10.1371/journal.pone.0225047

Table 4. Amount of total dust and bacteria obtained from air samplings.

Trial Season Week No. of animals Ventilation flow rate, UVC module (m3/h) Total dust
(mg/m3 ± SD)		 Total airborne bacteria
(cfu/m3 ± SD)
Barn 1 with UVC module Barn 2 (Reference) Barn 1 with UVC module Barn 2 (Reference)
1 Spring 0 0 na 0.014a 0.016 a 0b 0b
1 10 na 0.341 a 0.586 a 56,000b 290,000b
2* 10 416 0.599 a 0.477 a 93,000b 46,000b
3* 10 409 0.288 ± 0.206 0.581 ± 0.105 38,000b 140,000b
Summer 4* 10 385 0.485 ± 0.408 0.650 ± 0.126 48,000b 110,000b
5* 10 341 0.380 ± 0.207 0.458 ± 0.353 92,000b 320,000b
6 10 423 0.365 ± 0.003 0.131 ± 0.016 140,000b 420,000b
7 10 359 0.172 ± 0.115 0.513 ± 0.401 430,000b 750,000b
8 10 315 0.302 ± 0.130 0.367 ± 0.255 240,000b 620,000b
9 10 357 0.282 ± 0.146 0.228 ± 0.243 1,300,000b 1,100,000b
10 10 322 0.607 ± 0.301 0.230 ± 0.018 780,000b 540,000b
11 10 366 0.610 ± 0.323 1.340 ± 0.156 1,000,000b 310,000b
12 10 300 0.710 ± 0.595 0.879 ± 0.482 510,000 ± 42,400 570,000 ± 127,000
13 9 352 0.363 ± 0.263 0.738 ± 0.291 345,000 ± 63,600 820,000 ± 396,000
2 Summer 0 0 0 0.010 ± 0.005 0.004 ± 0.001 84 ± 23 40 ± 13
Autumn 1 11 405 0.468 ± 0.112 0.597 ± 0.144 287,000 ± 49,300 397,000 ± 130,000
2 11 405 0.200 ± 0.103 0.545 ± 0.117 81,000 ± 26,200 297,000 ± 66,600
3 11 357 0.295 ± 0.079 0.603 ± 0.186 73,700 ± 15,500 267,000 ± 102,000
4 11 387 0.667 ± 0.243 0.530 ± 0.055 94,300 ± 41,800 200,000 ± 60,800
5 11 402 0.548 ± 0.214 0.403 ± 0.113 91,700 ± 18,500 433,000 ± 222,000
6 11 392 0.643 ± 0.064 0.865 ± 0.250 190,000 ± 62,400 1,060,000 ± 661,000
7 11 394 0.672 ± 0.086 0.890 ± 0.249 187,000 ± 95,000 530,000 ± 303,000
8 11 393 0.848 ± 0.198 0.845 ± 0.207 141,000 ± 58,500 433,000 ± 115,000
9 11 402 0.999 ± 0.374 1.360 ± 0.262 190,000 ± 60,800 527,000 ± 246,000
10 11 420 0.572 ± 0.369 1.757 ± 0.567 53,700 ± 37,200 1,000,000 ± 195,000
11 11 392 0.817 ± 0.250 1.257 ± 0.176 217,000 ± 70,900 1,070,000 ± 405,000
12 11 422 1.281 ± 0.401 1.042 ± 0.548 260,000 ± 161,000 557,000 ± 169,000
13 11 383 1.327 ± 0.309 0.855 ± 0.699 250,000 ± 115,000 130,000 ± 98,900
Winter 14 11 427 0.831 ± 0.485 1.437 ± 0.367 80,000 ± 36,100 217,000 ± 37,900
15 11 441 1.440 ± 0.427 1.867 ± 0.540 460,000 ± 105,000 520,000 ± 504,000
16 11 456 1.320 ± 0.708 1.270 ± 0.480 410,000 ± 26,900 433,000 ± 90,700

Measurements were taken weekly. The ventilation flow rate at the UVC module was read at the beginning of each sampling day. Total dust values (mean ± SD) were calculated from data collected by the DustTrak™ DRX Aerosol Monitor over 10 min. Total dust comprises particles ≤1 μm, ≤2.5 μm, respirable particles, and ≤10 μm. The amount of total bacteria represents the mean ± SD of measurements done at three sampling locations (indicated as yellow stars in Fig 2). UVC intensity was between 1,100 and 1,280 μW/cm2. Seasons were defined according to the astronomical calendar: spring (21st March to 20th June), summer (21st June to 22nd September), autumn (23rd September to 21st December), winter (22nd December to 20th March).

na–Not applicable as the module had been installed the second week of the first trial.

*Climate control unit of the general ventilation system in barn 1 was defective.

a During the first two weeks of trial 1, dust was measured only at one sampling location.

bDuring the first trial, bacterial counts were measured only at one sampling location.