Did you know most vehicles have an air filter for the cabin? Ever change yours? Manufacturers recommend you do so every 15,000 to 30,000 miles. Now, before you start using the A/C regularly, would be a good time.
Micronair Car Filters has a list of vehicles with instructions for each model. It appears to be rather simple and most cost around $20-25, some more.
Amazon.com has them cheaper.
Big surprise, my ugly ol’ truck isn’t listed. Heh.