Aeroseal is a brand-name duct-sealing process. The installer blocks the registers, pressurizes the duct system, and releases an aerosolized sealant that's carried to the leaks, where it builds up and seals the gaps from the inside. The machine logs a leakage figure before and after, so the result is measured rather than claimed.
It addresses a different problem than cleaning. Leaky ducts waste roughly 20–30% of heating and cooling energy (ENERGY STAR) and cause hot-and-cold rooms. Sealing keeps conditioned air in the system, which can lower bills and even cut the equipment size you need.
Aeroseal isn't the only way to seal — a technician can also apply mastic or metal-backed tape by hand at accessible joints — but its selling point is the verifiable before/after number. If a provider offers sealing, ask for that measurement; a sealer who 'just sprays' without testing can't prove the leaks are gone. Sealing work also often qualifies for utility efficiency rebates.