The core idea of 85/85 tests is to quicken aging and moisture absorption by placing samples in a controlled chamber with 85°C and 85% relative humidity for a set time, often ranging from 500 to 1000 hours. Discover how an 85°C 85%RH constant humidity chamber works. Learn its applications in electronics, automotive, and material testing, plus key design features and testing processes. SIR stands for Surface Insulation Resistance and ECM stands for Electrochemical Migration. Both Surface Insulation Resistance and Electrochemical Migration tests are designed to determine the propensity for a material and/or process to lead to some sort of electrochemical event. The 85/85 test requires an environmental chamber with exceptional long-term temperature and humidity stability. Even minimal variations during the 1,000-hour test can invalidate the results. We have seen boards pass ROSE at 1.2 µg/cm² but fail SIR after 168 hours at 85°C/85%RH. The root cause was a combination of marginal cleanliness and an aggressive flux that left hygroscopic residues. Unlike simple temperature cycling tests, the 85/85 test specifically focuses on moisture-related degradation mechanisms. High humidity penetrates materials, interfaces, coatings, and packaging structures, while elevated temperature accelerates chemical reactions and material aging processes. A double 85 test chamber is a specialized type of Environmental test chamber designed to maintain precise conditions of 85°C temperature and 85% relative humidity over extended periods. The 85/85 test is critical for evaluating the durability and reliability of electronic components under extreme temperature and humidity conditions. By subjecting materials to extreme conditions in this test, manufacturers can identify potential failures early in their products’ life cycles. Complete guide to 85/85 testing (THB): how this reliability test works, why it matters, and how it compares to HAST testing for accelerated qualification. Double 85 testing is a steady-state damp heat test that holds a product at 85 °C and 85 % relative humidity, continuously, typically for 500 or 1000 hours. The combination is aggressive enough to drive moisture through seals, encapsulants and coatings, yet controlled enough to remain repeatable.