Temperature & Humidity Testing — Steady-State, Cyclic Damp Heat and Thermal Shock.

Climatic testing reveals how heat, cold and moisture degrade a product over its life — corrosion, condensation inside enclosures, insulation breakdown, thermal fatigue and dimensional change. The right test depends on the real environment the product will see: sustained tropical humidity, day-night condensation, or rapid swings between hot and cold. The main regimes below answer different questions, and most qualification programs combine them.

Steady-state damp heat (IEC 60068-2-78, Test Cab)

This test holds a constant high temperature and humidity — typically 40 °C and 93% RH, or 30 °C at 85–93% RH — for a fixed duration, commonly 10, 21 or 56 days. Conditions are reached within about two hours and then held without condensation, so the stress is sustained moisture rather than wetting. It exposes slow failure modes: moisture absorption, corrosion and gradual insulation degradation. Automotive programs often run a more aggressive variant such as 85 °C / 85% RH for 1000 hours (AEC-Q102).

Use it for: products that live in persistently humid, warm climates and must endure long exposure.

Cyclic damp heat (IEC 60068-2-30, Test Db)

Here the chamber runs a 24-hour cycle: a warm, humid phase, then a controlled cool-down to about 25 °C that deliberately drives condensation — dew — onto the specimen, repeated for a set number of cycles (commonly 2, 6, 21 or 56). Unlike the steady-state test, the point is the wetting: as the item cools it "breathes," drawing moist air and condensation toward seals and internal surfaces. It reveals condensation-driven ingress, surface corrosion and insulation faults that a no-condensation test would miss.

Use it for: equipment exposed to day-night temperature swings and dew, outdoors or in unconditioned spaces.

Temperature cycling and thermal shock (IEC 60068-2-14, Test N; MIL-STD-810 Method 503)

Both move the specimen between hot and cold extremes; the difference is the transition rate. Temperature cycling ramps gradually with a dwell at each extreme long enough for the item to stabilize. Thermal shock transfers the item between hot and cold zones rapidly — on the order of a minute — to maximize the thermal gradient. These expose thermal fatigue: cracked solder joints, delamination, seal failure and stress in dissimilar materials.

Use it for: products that face rapid thermal transitions or repeated heating and cooling in service.

The standards landscape

Two frameworks dominate, with the same physics but different selection logic. IEC 60068-2 offers standardized severities you select from — 60068-2-1 (cold), 60068-2-2 (dry heat), 60068-2-78 (steady-state damp heat), 60068-2-30 (cyclic damp heat), 60068-2-14 (change of temperature). MIL-STD-810 instead tailors the test to a deployment's life-cycle environmental profile, through Method 501 (high temperature), 502 (low temperature), 503 (temperature shock) and 507 (humidity). Sector standards such as AEC-Q102 (automotive) and the GB/T 2423 series (the Chinese counterpart to IEC 60068) build on the same methods.

Choosing — and combining

Match the test to the real environment: steady-state damp heat for sustained humid climates, cyclic damp heat for day-night condensation, and temperature cycling or thermal shock for transitions and thermal fatigue. The regimes are complementary and a single program often runs several — for example steady-state humidity followed by thermal cycling — to cover a product's full climatic life.

Testing with ULMEKA

ULMEKA designs climatic test chambers for these regimes — under PLC + HMI control with programmable temperature and humidity profiles, real-time monitoring and dew-point control. Whether your requirement is a severity under IEC 60068-2 or a method under MIL-STD-810, tell us the profile, the severities and your specimen dimensions, and we will propose a matched system.