An inflatable tunnel or air-inflated tunnel is a tunnel

Tunnel

A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...

 that is inflated by an external cold air inflation fan connected to the tunnel via an inflation tube. Inflatable tunnels are customarily 10' to 30' long when inflated and often attached to inflatable helmets, mascots or team logos.

Inflatable tunnels are typically used by professional, college and high school sports teams and first started appearing in the 1980s. One of the first inflatable team tunnels was used by the San Diego Chargers

San Diego Chargers

The San Diego Chargers are a professional American football team based in San Diego, California. they were members of the Western Division of the American Football Conference in the National Football League...

 in 1994. Most NFL teams use an inflatable tunnel for player introductions.