In general, the preservation of hand-coloured photographs is similar to that of colour and monochrome photography. Optimal storage conditions include an environmentally controlled climate with low relative humidity (approximately 30-40% RH), temperatures under 68 degrees Fahrenheit (20 degrees Celsius), and a low concentration of particulate pollution, such as sulfuric acid, nitric acid, and ozone. The storage area must also be clean and free of pests and mould. Because hand-coloured photographs, like colour photographs, are more sensitive to light and UV radiation, storage should be in a dark location. The storage area should be secure and monitored for internal threats – such as change in temperature or humidity due to HVAC malfunction, as well as external threats, such as theft or natural disaster. A disaster plan should be created and maintained for all materials.