# Room treatment

On average, a **36 watt bulb or light** (~12 watts real UVC emission) is **minimally** required to treat a small to average room. More wattage, means more effectiveness.

Required UV dose: 5,000 µJ/cm² for proper disinfection.

As you can see in the table below, the **inverse square law** says that intensity drops dramatically as the distance increases. Hence the requirement of high wattage to cover adequate space.

Above a 5 meter distance, there is **little effect**.

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### UVC Surface Disinfection - 36 W Lamp (12.2 W UVC Output)

**Formula (inverse-square law for hemispherical spread):**

$$
I(d) = \frac{P}{2 \pi d^2}, \quad t = \frac{D}{I(d)}
$$

Or: I(d) = P / (2 * pi * d^2),  t = D / I(d)

Where:

* (I(d)) = irradiance at distance (d) (µW/cm²)
* (P) = total UVC output of lamp (µW) = 12,200,000 µW
* (d) = distance from lamp (cm)
* (D) = required UV dose (µJ/cm²) = 5,000 µJ/cm²
* (t) = exposure time (seconds)

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| Distance | Intensity I (µW/cm²) | Time for 5 mJ/cm² |
| -------- | -------------------- | ----------------- |
| 20 cm    | 4,855                | ~1 s              |
| 50 cm    | 775                  | ~6.5 s            |
| 1 m      | 194                  | ~26 s             |
| 2 m      | 48.5                 | ~1.7 min          |
| 3 m      | 21.6                 | ~3.8 min          |
| 4 m      | 12.1                 | ~6.9 min          |
| 5 m      | 7.7                  | ~10.8 min         |

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### Memory jog of basic inverse square law:

$$
I(d) = \frac{I_0}{d^2}
$$

Or: I(d) = I0 / (d^2)

Where:

- I(d) = intensity at distance d

- I0 = intensity at reference distance (e.g., 1 m)

- d = distance from the source (same units as I0 reference)