General Info

• TH E FI E L D C O N T R O L S CO M P AN Y •

Intensity Of The Light Diminishes Over Distance

UV rays are predominantly emitted perpendicular to the surface of the lamp. In order to determine the intensity of ultraviolet radiation on a

surface at different distances from a UV lamp, multiply the intensity of the lamp rating at 1 meter (microWatts per square centimeter) by the

intensity factor opposite the distance selected as shown below. This table provides an easy method for quickly calculating ultraviolet intensity.

For example, to determine the ultraviolet intensity produced by one 37 microWatt lamp rating at 1 meter at a distance of 6 inches from the

lamp, multiply the rated intensity of the lamp, by the intensity factor given opposite 6 inches, which is 20:

37 X 20 = 740 microWatts/cm

Maximizing Exposure To UV

Since UV rays are primarily emitted perpendicular to the surface of the lamp, lamps should be located at right angles to the air flow, so that

the rays are emitted parallel to the airflow. This will maximize the exposure time for airborne bacteria as they flow through the HVAC duct

system. Placing a lamp on the duct wall parallel to the airflow decreases the area of transmission of the radiation to only the width of the

duct. Placing a lamp in a tube restricts the UV radiation to only the air passing through the tube.

Distance from Lamp (Inches) Intensity Factor

0 354

1 127

2 69

4 32

6 20

8 14

10 14

15 6

20 4

25 3

30 2

35 1.4

39.37 (1 meter) 1

FIGURE 2

AIR FLOW

FIGURE 3

Most Effective:

When the lamp is located at right angles to the air flow,

airborne bacteria is irradiated for the longest period of

time (see shaded area).

Less Effective:

When the lamp is located on the duct wall parallel to the

air flow, air is irradiated only while passing the short

distance along the lamp (see shaded area).

Least Effective:

When the lamp is located in a pipe or tube, only the air

that passes through the tube is irradiated (see shaded

area).

Unit Intensity at 1 meter

UV-12 37 mW/cm

UV-18 73 mW/cm

AIR FLOW