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Archived noindex page. Kefiw's public focus is Property decision help.

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This older Kefiw page is kept for reference, marked noindex, and removed from the primary sitemap. The current Kefiw experience is focused on property decisions: cost, quotes, damage, buying, selling, owning, and packets.

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UV Exposure Delta · Fitzpatrick MED

Burn time by Fitzpatrick skin type, UV index, and applied SPF.

Minimum Erythemal Threshold (MED) varies by Fitzpatrick type — type I burns at 200 J/m², type VI at 1000 J/m². At UV Index 1 ≈ 25 mW/m² erythemally weighted, burn_min = MED / (UVI × 1.5).

Part of: Environmental Stressors

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Fields marked optional can be skipped; results update as you type
UV Exposure Delta · Fitzpatrick MED
Risk Level · UV 7
High
Unprotected burn time
24 min
to 1 MED (erythema onset)
Protected burn time
11.9 h
w/ SPF (ideal application)
Burn time = MED / (UVI × 1.5) min. SPF multiplier assumes ideal 2 mg/cm² coverage — real-world application typically delivers ¼ to ½ of labeled SPF. Re-apply every 2h or after swim/sweat.

How to use

  1. Enter current UV index (from weather), pick skin type, enter SPF applied.
  2. Read unprotected burn time and the SPF-multiplied protected window.

Examples

UV 7 · Type II · SPF 30
Unprotected 24 min to MED · protected 12 h — if you reapply every 2 h.

Before you act on the result

Health-related tools are educational planning aids. They can make a number or assumption visible, but they do not diagnose, treat, prescribe, or replace clinician guidance.

If the result points to risk, symptoms, medication questions, or urgent changes, use it as a note for a qualified professional rather than a final decision.

Next up

Sun logged. Now model the heat failure point.Thermal Failure · WBGT → Outdoors long? Layer for the temperature swing.Insulation Logic · Clo Units →

Frequently asked questions

› Does SPF really multiply burn time?

In lab conditions (2 mg/cm² application). Real-world application delivers ¼ to ½ of labeled SPF. Reapply every 2 h.

› Is tan cumulative? Trust & accuracy

MED resets overnight. Melanin buildup (tanning) does push MED slightly over weeks — but at the cost of DNA damage.

Tips & related reading

See the Environmental Stressors hub →

Tips & how-tos

Relevant links

Related tools

Thermal Failure · WBGT

Wet-bulb globe temperature — the heat-stress index used by OSHA, ACGIH, and military for work/rest cycle decisions.

Insulation Logic · Clo Units

Required clothing insulation in clo units for air temperature and activity level. Suggested garment stack.