The test took place in August at an operation in the Shanxi Province near Shouzhou and involved a pre-constructed Strata Safe Room. The individuals were enclosed in the explosion-proof shelter, which was set up over 6,100 meters (3.8 miles) from the entrance, for 48 hours.

The chamber included a back-up borehole from the surface for the supply of compressed air, liquid food and water as well as video equipment and power to the occupants to sustain the group for an indefinite period of time.

“Strata’s proprietary air-powered life support breathing air systems performed exactly as designed to keep air quality at safe levels and three newly developed designs for powerless cooling systems were tested independently to regulate internal temperatures,” Strata Worldwide engineering vice president John Reinmann said.

“As with our 96-hour fully manned chamber test performed earlier this year, this most recent live testing has provided an excellent opportunity to gather firsthand data. These tests not only prove the effectiveness and reliability of our systems, but also provide valuable information for Strata to continue enhancing its line of refuge alternatives.”

All 100 test participants, including the mine’s manager, exited the room after two days in good, stable health.

Strata said in July that it had completed its first fully-manned 96-hour underground test of its Strata Safety Inflatable Fresh Air Bay with partner China Coal Comprehensive Utilization Group at Shendong Coal’s Da Liu Ta operation in Shenmu County in the Shaanxi Province.

It was the largest underground manned test performed in the world to date.

The 16-man chamber was fully occupied at the active mine, and all testers remained for 96 hours. All of the unit’s life support systems were used as intended, Strata said, and each system performed as it was designed to meet China’s stringent standard requirements.

Strata’s Safe Rooms, designed for post-emergency protection and to provide breathable air and life sustaining supplies to miners trapped underground, also feature multiple airlock entrance compartments equipped with purge air, air curtains and passive carbon dioxide scrubbing systems.