Systems employing the simultaneous discharge of different agents to protect the same enclosed space shall not be permitted.

• A. Not permitted
• B. Permitted with AHJ approval
• C. Permitted if AMDQ adjusted
• D. Permitted if agents are compatible

Answer: (D)

The key idea is chemical compatibility of the agents. When two clean agents are released at the same time into the same enclosed space, they mix, so it’s essential that they do not react with each other to form toxic byproducts or otherwise reduce each agent’s effectiveness. If the agents have been demonstrated to be compatible for use together in the same enclosure, the system can be designed to meet the required protection performance with both agents active. If they are not compatible, simultaneous discharge could create hazards or compromise fire suppression, which is why it’s not permitted. Therefore, simultaneous discharge is permitted only if the agents are compatible, rather than requiring AHJ approval or adjusting an AMDQ parameter, which do not address the core issue of chemical interaction.