> ## Documentation Index
> Fetch the complete documentation index at: https://docs.appliedaifoundation.org/llms.txt
> Use this file to discover all available pages before exploring further.

# UV Intensity Thresholds

> The three key UV intensity levels used for compliance checking, operational targets, and lamp efficiency tiers.

## The three UV intensity thresholds

All three values are defined in `lib/constants.ts` under `THRESHOLDS.UV_INTENSITY`:

| Threshold  | Value        | Source             | Purpose                        |
| ---------- | ------------ | ------------------ | ------------------------------ |
| `IMO_MIN`  | **252 W/m²** | IMO G8 guidelines  | Minimum for IMO D-2 compliance |
| `USCG_MIN` | **530 W/m²** | 33 CFR Part 151    | Minimum for USCG compliance    |
| `OPTIMAL`  | **650 W/m²** | System design spec | Full-rated output target       |

## How 252 W/m² is used

The `IMO_MIN` value is the **primary compliance gate**. Any BALLAST or DEBALLAST operation where `UVR_INTENSITY < 252` represents a D-2 non-compliance event. In the dashboard:

* **Compliance tab**: IMO D-2 item shows red (NON-COMPLIANT)
* **Compliance tab treatment bar**: fills to `UVR_INTENSITY / 252` — when below 100%, compliance is at risk

## How 530 W/m² is used

The `USCG_MIN` is the **secondary compliance gate**, relevant for vessels operating in US waters. Between 252 and 530, the system is in a "marginal zone":

* IMO D-2 compliant ✅
* USCG non-compliant ⚠️

The Compliance tab shows the USCG item as WARNING (yellow) in this range. The USCG treatment bar fills to `UVR_INTENSITY / 530`.

## How 650 W/m² is used

The `OPTIMAL` value represents the system's full rated output under ideal conditions. It is used as:

* The denominator for efficiency calculations where intensity is expressed as a percentage of optimal
* The reference point for the UV Health component of the health score

Values above 650 W/m² are possible in cold, clear water conditions where UV transmittance is high.

## Operating zones

```
0 ────── 252 ─────────── 530 ──────── 650+ W/m²
  FAIL    │  IMO ONLY    │  BOTH OK  │  OPTIMAL
          │              │            │
```

## Lamp efficiency thresholds

Separate from UV intensity, individual lamp efficiency is tracked against these tiers, defined in `THRESHOLDS.LAMP_EFFICIENCY`:

| Tier     | Efficiency range | Colour | Recommended action                |
| -------- | ---------------- | ------ | --------------------------------- |
| GOOD     | ≥ 90%            | Green  | No action                         |
| WARNING  | 70–89%           | Yellow | Monitor, plan future replacement  |
| DEGRADED | 50–69%           | Orange | Schedule replacement at next port |
| CRITICAL | \< 50%           | Red    | Urgent replacement required       |

## Lamp runtime thresholds

Defined in `THRESHOLDS.LAMP_RUNTIME`:

| Threshold | Value       | Action                     |
| --------- | ----------- | -------------------------- |
| `WARNING` | 2,500 hours | Begin planning replacement |
| `MAX`     | 3,000 hours | End of rated lamp life     |

## UV intensity vs lamp efficiency: the relationship

Individual lamp efficiency affects aggregate `UVR_INTENSITY`. As lamps degrade, the system cannot maintain the intensity setpoint without increasing `UVR_POWER_OUTPUT`.

`POWER_COMPENSATION_PCT` quantifies this: a value of 20 means the system consumes 20% more electrical power to achieve the same UV intensity that new lamps would produce at rated power. This is visible in the Trend Analysis tab's runtime charts — the power line climbs as the efficiency line falls.

## References

* [IMO D-2 Regulation](/concepts/imo-d2-regulation) — regulatory context for the 252 W/m² threshold
* [USCG Standards](/concepts/uscg-standards) — regulatory context for the 530 W/m² threshold
* [UV Disinfection Technology](/concepts/uv-disinfection) — physics behind intensity requirements
* [Compliance Monitoring Tab](/product/compliance-tab) — where these thresholds are applied in real time