Chlorine was traditionally used in paper making as a bleaching agent. This is less common now but some older plants may well still use it. Fixed chlorine systems may still be required. Likewise SO2 detection is also needed within the process. The process engineers and safety department will be interested in the fixed and multi channel portables as well as SGT-P for the target gases.
Most paper mills also have their own waste treatment plants. This will need multi channel portables for all the same confined spaces gases found in the water industry. The treatment plant is often run as a separate entity and the contact to speak to is the treatment plant manager.