Box Fans can be an important tool for forced ventilation and for emergencies.  When combined with various filter configurations or used in windows a simple fan like this can broaden your capabilities.  

• 20in. box fan with 3 speeds engineered for ample air flow
• Compact and lightweight with built-in handle for easy transport
• Energy-efficient fan helps keep you feeling cooler while spending less than 2¢ per hour to operate
• Easy-to-use top-mounted control knob
• Features The Blue Plug trusted, safety fuse technology
• Safe, rounded corners
• Simple no-tools assembly
• Use in conjunction with an air conditioner to boost cooling airflow
• Use in conjunction with a MERV Carbon Filter to boost air quality
• ETL listed

Put it in a window, on the floor in a bedroom, living room, office or anywhere you need a fan. Comes with a 1-year limited warranty