Results And Discussion - Stadler Form Roger Operating Instructions Manual

5. Results and Discussion

The recovery concentrations of Inf A in the three inactive control runs and the three active test runs
are reported in Tables 5.1 and 5.2. Each result is the average of three replicates sampled at the
indicated time. The Inf A concentration was determined by ELISA in units of ng/ml and then
converted into ng/m , i.e. nanograms of Influenza A per cubic metre of air sampled by the SKC
3
BioSamplers.
Table 5.1. Average Influenza A concentration measured in the inactive
Timepoint
-10 – 0
5 – 15
20 – 30
50 – 60
Table 5.2. Average Influenza A concentration measured in the active test
Timepoint
-10 – 0
5 – 15
20 – 30
50 – 60
Figures 5.1 and 5.2 show the trend of Inf A levels over time in the three control and test runs,
respectively. The rapid reduction in Inf A concentration observed in the test runs (Figure 5.2) could
not be attributed to natural decay due to forces exerted on the virus particles, i.e. inertia, diffusion.
In the three test runs, between 50 and 60 minutes of the air purifier operating, the Influenza A
concentration had dropped below the detection limit of the assay used to quantify the virus. The
differences among the same sampling time points in the runs can be ascribed to the virus stock
used to perform the runs and the sampling process itself. As reported by Fabian et al. in 2009, for
laboratory studies SKC BioSamplers represent the most efficient airborne virus particle sampling
tool in terms of virus infectivity preservation and collection efficiency. Despite this, the BioSampler
recovery efficiency is about 79% for particles sized > 0.3 µm, which may lead to variation in the
collected concentrations of Inf A particles sized ~ 0.1 µm.
ASCR092436
control runs (ng/m
Control 1 Control 2
2729.1 3447.4
2099.3 1973.9
1546.7 1511.5
874.9 773.3
Test 1 Test 2
3800.9 3594.9
188.4 147.5
67.5 164.0
<LOD <LOD
<LOD: Less than the limit of detection
Page 6 of 10
)
3
Control 3
3900.1
2770.5
2294.5
1386.7
runs (ng/m )
3
Test 3
3898.4
231.5
85.1
<LOD
Average (n=3)
3358.9
2281.2
1784.2
1011.6
Average (n=3)
3764.7
189.1
105.5
<LOD
FM1201