Final answer:
The specific minimum depth for decompression chamber certification is not provided in the reference material, but such chambers are crucial for safely treating scuba divers with decompression sickness by simulating the necessary depths for controlled recompression.
Step-by-step explanation:
The minimum depth to which a decompression chamber must be blown down for certification is not explicitly stated within the provided reference material. However, decompression chambers and recompression therapy are critical in treating decompression sickness (DCS) that can occur when scuba divers ascend too quickly from depth, decreasing the ambient pressure too rapidly which allows gases dissolved in the body to come out of solution and form bubbles. These pressurized vessels must be capable of simulating various depths to effectively and safely treat divers with DCS by re-pressurizing the body and allowing for a controlled decompression, enabling the gases to dissolve back into the body's tissues safely.
Each decompression chamber's certification requirements may vary based on country and industry standards, taking into account safety regulations and medical guidelines. To determine the specific minimum blow down depth for certification, you would need to consult the certifying body's standards and regulations for hyperbaric therapy equipment.