mma26:
The National Medical Standards state: "A medical condition that would preclude a person from performing as a firefighter in a training or emergency operational environment by presenting a significant risk to the safety and health of the person or others" as a bar to employment for someone with your specific handicap (partial deafness).
That is pretty specific. With your SSD (Single Sided Deafness) it would seem to disqualify you for a career as a firefighter. The Americans with Disability Act was meant to protect those with medical conditions or physical limitations that did not affect their performance from being disqualified from a job or profession. One-sided hearing obviously would affect your capability to perform all the functions of a firefighter as it impacts your ability to (as an example) discern sound direction and/or hear feint cries for help in a burning building or to misunderstand instructions from the Captain coming through a static-filled radio during a rescue mission. You could probably function as a dispatcher or other position that compliments firefighters but I doubt you'll have much success trying to find a loophole in the quite reasonable medical standards.
You might want to consider scheduling a consultation with an attorney who handles such cases. To find one, contact your local bar association...they're in the phone book. If he concurs with my opinion, you'll at least know for sure that this particular field is closed to you and be freed to pursue a different career...preferably one that doesn't require excellent hearing in both ears.
I wish you well and, although this is probably not what you wanted to read, I hope the advice is useful to you.
Jim