222
Calculation example
This is an example of how to calculate disinfection time and ultraviolet Far-UV-С (222 nm) intensity versus distance from the light source.
Studies have shown that complete deactivation of COVID-19 requires about 2 mJ/cm2.
First, we calculated the dose of ultraviolet radiation, and then checked the results with a dosimeter.
The calculation used an excimer module KVP-GM-FARUV-150 with the following specification:
- Power: 150W
- UV radiation: 88 μW/cm²
- Wavelenth: 222 nm
Room dimensions: 8m x 6m
Lamp installation height 2.5 m
Calculation objects: horizontal planes 1m, 1.5m, 2m and 2.5 m from the Far-UV-C source.
1
1 m
Distance from the lamp to the measured surface is 1m
Maximum radiation dose is 87,9 μW/cm2 or 0.0879 mJ/cm2
It takes 23 seconds to reach 2 mJ/cm2
1.5
1,5 m
Distance from the lamp to the measured surface is 1,5m
Maximum radiation dose is 39,6 μW/cm2 or 0.03960 mJ/cm2
It takes 50,5 seconds to reach 2 mJ/cm2 or for about a minute
2
2 m
Distance from the lamp to the measured surface is 2m
Maximum radiation dose is 22,5 μW/cm2 or 0.02250 mJ/cm2
It takes 89 seconds to reach 2 mJ/cm2 or for about 1,5 minutes
2.5
2,5 m
Distance from the lamp to the measured surface is 2,5m
Maximum radiation dose is 14,5 μW/cm2 or 0.01450 mJ/cm2
It takes 138 seconds to reach 2 mJ/cm2 or for about 2,5 minutes
222
Pivot table
|
Distance from the lamp
|
Calculated Far-UV-C dosage μW/cm2
|
Measured Far-UV-C dosage μW/cm2
|
Disinfection time by getting 2 mJ/cm2
|
|
1 m
|
87,9
|
88
|
23 sec
|
|
1,5 m
|
39,6
|
39,1 |
55,5 sec / 1 min
|
|
2 m
|
22,5
|
22 |
89 sec / 1,5 min
|
|
2,5 m
|
14,5
|
14 |
138 sec / 2,5 min
|
Calculations show that with a change in distance, the dose of ultraviolet radiation and, accordingly, its effectiveness decreases rapidly. Therefore, the exact dimensions of the room and the position of the installed UV sources are necessary to accurately calculate the number and wattage of the lamps, as well as the required sterilization time.
Measurements with the dosimeter showed an extremely small error between the calculated and measured data. However, we strongly recommend using a dosimeter to check the calculated data.