I bought the MERV filter to use in the ceiling air intake of my central AC system. It works fine. Before replacing the plastic mesh filter that was there, I thought the MERV filter might slow the air flow. It didn't. The cool air comes through as strong as ever, and cleaner.
I have a couple dogs & terrazzo floors so I change my filters every 30 days. I started using these filters last year when I first purchased this home and added central air. A year later it still smells fresh walking in Im sure its due to good filters helping me to keep it clean.