Humidity Testing

Humidity testing holds a product at a controlled relative humidity, usually at an elevated temperature, to find the failures moisture causes over time: corrosion on contacts, absorbed water in plastics and boards, leakage paths across insulation, and condensation inside a sealed enclosure. We support a variety of humidity methods, including IEC 60068-2-78 and IEC 60068-2-30 damp heat, MIL-STD-810 Method 507 and RTCA DO-160 Section 6, and we can test to your own specification too. Megalab runs humidity testing up to 98 % RH, accredited to ISO/IEC 17025 by A2LA.

Water vapour goes where air goes. A product that passes a dry heat test can still fail once humidity is added, because moisture drives a different set of mechanisms.

• It corrodes. Contacts, connector pins and plated surfaces oxidise faster in warm, wet conditions, and a corroded contact fails intermittently long before it fails outright.
• It gets absorbed. Plastics, laminates and printed boards take on water, which changes dimensions, lowers insulation resistance and can cause popcorning at a later high temperature step.
• It condenses. When a warm, humid product cools, water forms on internal surfaces. A sealed enclosure does not prevent this if humid air was inside when it was closed.
• It creates leakage paths. Enough surface moisture and a high impedance node stops being high impedance, which shows up as drift, false triggering or a failed insulation test.

Both appear in specifications as damp heat and they are not interchangeable.

• Steady state damp heat (IEC 60068-2-78 Test Cab) holds a constant elevated temperature and constant high humidity for the duration. It measures the cumulative effect of long exposure, and it is the right test for absorption, corrosion and insulation degradation.
• Cyclic damp heat (IEC 60068-2-30 Test Db) cycles the temperature while humidity stays high. Each cool down drives condensation into the product and the temperature swing acts as a pump. It is markedly more severe than steady state at the same nominal humidity, and it is the test that finds breathing enclosures and marginal seals.

If your specification says damp heat without saying whether the temperature cycles, it is ambiguous. Send it and we will tell you which one it describes. 85/85 is the common industry shorthand for 85 C and 85 % RH steady state, usually written into a customer specification rather than a published standard. We run it under the same accredited technology as the IEC methods.

• Steady state damp heat: IEC 60068-2-78 and MIL-STD-810 Method 507 Procedure I.
• Cyclic damp heat: IEC 60068-2-30, IEC 60068-2-38 and MIL-STD-810 Method 507 Procedure II.
• Moisture resistance: MIL-STD-202 Method 106 and MIL-STD-883 Method 1004, the component and microcircuit equivalents.
• Accelerated ageing: ASTM F1980, using temperature and humidity together to represent shelf life.
• Condensation and dew point exposure where the requirement is specifically to form water on the product.

For a sealed product, humidity testing is usually run alongside ingress protection testing, because the two answer different questions about the same enclosure: whether water gets in from outside, and whether moisture already inside does damage.

We run a variety of humidity chambers, from bench-scale reach-ins up to walk-ins that take a forklift-loaded pallet or a complete assembly, so a product is tested at the size it ships rather than cut down to a coupon. Across that fleet, accredited humidity testing holds up to 98 % relative humidity, at temperatures above 15 C. A few of the chambers are temperature only and cannot hold humidity at all, so a combined profile is scheduled into one of the units that can.

Every humidity chamber has port access through the wall for power and instrumentation, so a sample runs powered and monitored throughout rather than being checked before and after. The walk-in chambers take humidity profiles at full size, which is unusual, so a rack, a pallet of packaged product or a complete machine can be held at controlled humidity. The humidity ceiling is lower at walk-in scale, so send us the dimensions with the profile and we will confirm which chamber it books into before you ship anything.

Accredited by A2LA to ISO/IEC 17025 under certificates 5179.01 and 5179.02. See our accreditations.

• The standard and method, or your internal specification
• The temperature and relative humidity setpoints, and whether the profile is steady or cyclic
• How long the exposure runs, since humidity programmes are booked as continuous chamber time
• Sample dimensions, weight and quantity
• Whether the product is powered or monitored during exposure, and what needs to pass through the chamber wall
• Whether you need insulation resistance, functional or visual checks, and who performs them

Send us the specification and we will confirm the requirement and quote it.