1. Age of Ductwork: If your ductwork is more than 15-20 years old, it might be nearing the end of its lifespan, especially if it hasn’t been properly maintained or inspected regularly.

2. Visible Damage: Inspect your ductwork for visible signs of damage such as cracks, holes, rust, or corrosion. These can indicate wear and tear that compromises the efficiency of your HVAC system.

3. Inconsistent Temperatures: If you notice inconsistent temperatures throughout your home or building, it could be a sign of ductwork leaks or blockages, leading to uneven airflow.

4. Increased Energy Bills: Leaky or poorly insulated ductwork can cause your HVAC system to work harder to maintain the desired temperature, resulting in higher energy bills.

5. Excessive Dust or Debris: If you frequently notice an accumulation of dust or debris around your vents or registers, it could be a sign of leaky ductwork pulling in air from unconditioned spaces like attics or crawl spaces.

6. Unpleasant Odors: Mold, mildew, or musty odors emanating from your vents could indicate moisture buildup within your ductwork, which can lead to mold growth and poor indoor air quality.

7. Noisy HVAC System: Excessive noise coming from your HVAC system, such as rattling, banging, or whistling noises, could indicate issues with your ductwork, such as loose connections or obstructions.