The Cool Boss Tempest and Windstorm Series HVLS Industrial Ceiling Fans are designed to deliver optimized temperatures and air circulation in large interior spaces while reducing energy costs. The high-volume, low-speed (HVLS) fans are available in a range of sizes, from 11.5' to 24' in diameter. They’re quiet, using high-strength, fatigue-resistant aluminum alloy for the blades. The blades are powder coated to ease cleaning and ensure long life. The Tempest Series has two models (CB-11HVLS and CB-16HVLS), both of which have six blades. The Windstorm Series includes two five-blade models: CB-20HVLS and CB-24HVLS. Both Windstorm fans feature a built-in ion generator air purification system to improve air quality.