As I said - disability benefits are generally taxable.
There are two situations when disability benefits would not be taxable:
-- if that is a service-connected disability - conditions for such exclusion are listed above.
-- if payments are made under workers' compensation act of similar provisions.
Please be aware that answers posted on that site are for general information, and are not intended to substitute for informed professional advice and do not establish a professional-client relationship.
Thus I may help you to determine if your benefits are taxable and provide references to IRS sources, but I am not in the position to make a determination.
Based on facts that your provided - "retired from the FD due to an illness directly related to the fire service" - I assume that all or part of your benefits are similar to workers' compensation and generally are not taxable.
The administrator of your pension fund should issue a form 1099-R - www.irs.gov/pub/irs-pdf/f1099r.pdf which reports your disability benefits.
Your gross benefits should be reported in the box 1, and taxable portion in the box 2a.
If your benefits are not taxable - in the box 2a you will have zero.
Please be aware that the same information is provided to the IRS - so if the administrator reports your benefits as taxable and you disagree with such determination - that should be discussed with your administrator.
Let me know if you need any help.