First of all, sorry to keep you waiting. This is a very tricky question. The rules are easy to explain but difficult to apply. Let’s start with PPE. Your obligation is to make reasonable accommodations for the worker’s hearing disability to the point of undue hardship. To figure out what to do with this individual, you need to engage them in an accommodations process to determine their needs. Don’t speculate as to what damage X kind of PPE will do. Ask the employee. You can also require reasonable verification of the hearing impairment–assuming you have doubts as to whether it really exists. You may also require the person to undergo medical evaluation.
As for emergency response, it’s your responsibility to ensure that your evacuation and response plan and procedures accommodate the needs of individuals with disabilities. For the hearing impaired, that may require lights or strobes instead of alarms. Again, it all depends on the individuals, their abilities/disabilities and their needs. Hope that helps. Glenn