At our site we have a cogen unit fueled by natural gas in our power house that runs to help mitigate power costs at high peaks. It has a CO2 extinguishing fire protection built in that senses high temperature and shuts down the unit and deploys CO2 gas. Recently we found this protection system left locked out at a isolation point after it was serviced a few days before. We will be conducting an investigation as to how this was missed, one of my questions will be why wasn't this new cogen fire suppression extinguishing system tied to our site Fire Alarm panels that would have left a supervisor or maintenance alert. Is there a NFPA code requirement?