It's all go on the Pike River mine re-entry with the 170-metre barrier being breached on Tuesday morning.
Tests have shown the atmosphere in the drift is stable and Recovery Agency chief operating officer Dinghy Pattinson says four people are going in.
"We'll be doing a hazard and Geotech assessment of the roof and walls to make sure the ground's stable as we proceed in, and we'll also do a forensic scan," he told Newshub.
The recovery team was given the green light to go further into the mine's drift earlier this month.
They've previously gone 170m in - but Tuesday's move will see them going beyond that for the first time.
"We've monitored the environment underground for the last seven days and that's proven we've got a stable, steady, safe atmosphere underground, so that allows us today [Tuesday] to do what we want to do," said Pattinson.
The barrier will be breached between 10 and 11am. Pattinson told Newshub the maximum distance they can travel is 20m per shift or 40m per day.
"We know we're only going to go about 15m because there is an area that requires roof support from 15m on, so we'll barricade it off at that area and do the forensic search [and] scan in that area we're in," he said.
The next phase will see a push through the remainder of the 2.3km drift, with forensic examinations happening along the way.
"We need to find out as much as possible about what caused 29 men to go to work and not come home," Minister responsible for Pike River re-entry Andrew Little said earlier this month.
"Now the agency will proceed with what it considers to be the best and safest way to ventilate the drift."
In October, thirty family members took the opportunity to visit the 170m seal drift.
The family members went the furthest they'd ever been allowed into the mine.
