If you are under 60 years of age as of December 31, 2020, then only employer pensions are eligible for the Pension Exclusion.
If you are over 60 years of age as of December 31, 2020, then employer pensions, income from qualified retirement plans (IRA, 401(k), Keogh plans, government deferred compensation plans, etc), dividends, capital gains, interest, and net rental income from real property, are eligible for the Pension Exclusion.
An early distribution from an IRA or pension fund for emergency reasons or following a separation from employment does not qualify for the Pension Exclusion. If the distribution code listed in Box 7 of your 1099-R is a 1, or if you were assessed an early withdrawal penalty on Federal 1040, Line 59 for the distribution, then that distribution DOES NOT qualify for the Pension Exclusion.
Distributions with code C or codes C and D (for reportable death benefits) in box 7 of the 1099-R also don't qualify.