Preparations are on track to venture further into the Pike River Mine drift by the end of September.
An execution plan for going beyond the 170 metre barrier is yet to be submitted to WorkSafe, but Recovery Agency Chief Executive Dave Gawn says atmospheric testing has been positive.
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"Most importantly, [we're] ensuring we can keep the atmosphere inside the mine," he told Newshub. "Well below anything that is flammable or explosive.
"As we go we learn more about the mine, and how it actually responds to what we do to it."
The 30 metre seal is being completely dismantled, to allow heavy machinery in.
"We're starting to get some real confidence in terms of some of the gas or atmospheric testing underground," Gawn said.
"It's progressing well, and we've got a little bit more drilling to do."
The mine was finally re-entered in May, weeks after it was delayed by faulty equipment and nearly a decade after the initial explosion.
Twenty-nine men, ranging in age from 17 to 62, were killed after several explosions in the mine in November 2010.
It was New Zealand's worst mining disaster since 1914.
Newshub.
