When you dive not just for recreational purposes and is already beyond normal scuba diving conditions, it will fall under technical diving. To ensure your safety, you need the necessary diving equipment and accessories for technical diving as well as additional training and experience.
Compared to recreational diving where you use only one scuba tank, twin cylinders or closed-circuit rebreathers are needed for tech divers.
Here are other scuba equipment and gear backups to make technical diving safe and productive.