One of the primary advantages of dark glass airtight containers is their ability to protect contents from light exposure. Light, especially ultraviolet (UV) rays, can lead to the degradation of many substances, particularly food items, essential oils, and herbal products. For instance, light can cause fats to turn rancid and degrade the vitamins and nutrients in foods. By using dark glass containers, you are providing a shield against these harmful rays, thereby increasing the shelf life and maintaining the quality of your stored items.