Poulan Pro 2250, 2450, 2550, 2550 SE, 2555 Instruction Manual page 18

The information on the product label indicates which standard your engine is certified.
Example: (Year) EPA Phase 1 or Phase 2 and/or CALIFORNIA.
This engine is certified to be emissions compliant for the following use:
Moderate (50 hours)
Intermediate (125 hours)
Extended (300 hours)
18