How long does one can last?

Duration depends on how often you spray and cabin ventilation. One application typically refreshes a vehicle interior for several hours. For consistent freshness, keep one can in your vehicle and use as needed.

Can I use this on upholstery and carpets, or just the air?

This is formulated as an air freshener spray. Test on a hidden area of fabric first if you plan to apply directly to seats or carpet — aerosol products can sometimes stain or over-saturate certain materials.

Will this damage dashboard or plastic trim?

Spray into open air rather than directly onto plastic or rubber components. If overspray contacts dashboard, wipe it down immediately with a dry cloth to avoid potential finish issues.