Photostability chambers provide high intensity lighting in the 300-700 nm range for pharmaceutical stability studies conducted at constant temperature (25°C) according to ICH guidelines. Each shelf has a bank of 10 lights that produce uniform lighting (±10%) across a large circular area on the shelf. The banks combine black and cool white fluorescent bulbs to satisfy the ICH definition for Option II lighting. At a distance of about 8″ from the lights, average light intensity is approximately 10,000 lux for visible light and 10 w/m2 for black light. Four light switches control the light banks, and four black light switches (or an optional timer) allow the black light portion of the testing to be curtailed while the visible light portion of the study continues to completion. Temperature failsafes and lockable solid doors (or optional tinted, mirrored glass doors) protect the study from temperature excursions and light disruption. Accessories such as an A/V hi-low alarm, chart recorder, or access port for remote monitoring are popular options.