Final answer:
Sprinkler system obstructions must be checked every five years to ensure functional fire safety measures in accordance with NFPA guidelines.
Step-by-step explanation:
The presence of obstructions in sprinkler systems should be checked every five years. This is a crucial safety measure to ensure that the sprinkler system functions effectively in the event of a fire. Inspections should be thorough and performed by qualified professionals to identify any potential blockages, corrosion, or other issues that might impede the operation of the sprinkler heads. It's important to adhere to the guidelines set by the National Fire Protection Association (NFPA) or local fire safety codes when scheduling these inspections.