Cave gate

[1] In the United States, an "industry standard" for gate construction has been developed.

Fish and Wildlife, Bureau of Land Management, U.S. Forest Service, The Nature Conservancy, National Speleological Society and others.

This standard focuses on proper gate placement that does not hinder airflow that would change a cave's micro-ecosystem.

[1] The industry standard or "Basic Gate Design" is a vertically placed flat grid of horizontal bars.

The spacing of the bar grid is crucial to allow access of small animals, such as bats, but restricting human entry.