The inquest into the Lakeland Mills explosion was taken through the measures incorporated into the new sawmill aimed at preventing a similar disaster in the future.
Gerhard Mikolajczyk, who was the lead design engineer on the project, said the intent was to reduce all five factors behind a blast - fuel, oxygen, ignition, compression and dispersion - as well as add features to protect employees in the event of a fire or explosion.
Much of that work centred on dealing with sawdust, identified by a WorkSafeBC investigation as the fuel that led to the April 23, 2012 blast that left two men dead - Glenn Roche and Al Little - and injured 22 others, many seriously.
Reducing the number of spots where sawdust can accumulate was done in a handful of ways.
So-called "shedder plates," made of thin-gauge metal, cover the bottom half of steel I-beams so that dust slides off. Moreover, beams made of engineered wood with no surface where dust can settle are used for the main sawmill's ceiling. Likewise, cross bracing is diamond-shaped.
In the lunchroom and administrative offices, the T-bar ceilings hold "egg crate" panels - effectively screens instead of solid boarding - so that dust cannot build up in areas between the roof and ceiling.
Cable trays remain in place but are wide enough to provide space between the cables so there's less chance of dust gathering.
All the booths and offices either have peaked roofs or extend all the way up to the ceiling and rather than the usual practice of placing them on the inside of the building, window ledges are on the outside while they're flush-mounted on the inside.
A centralized vacuum system was installed with a piping system running throughout the facility with hose connection spots so that the dust can be sucked away as oppose to simply being blown into a new location.
Lakeland had been looking at buying such a system and, 11 days before the blast, a sales representative for one brand had visited the facility.
As in the old mill, a separate dust collection system meant to pick up dust at the sawblade, as well as at the debarker is also in place. This time, it features three baghouses each connected to a particular section of the operation.
The baghouses are interlocked so that if one goes down, the section it's connected to also stops operating. And they can run round the clock seven days a week if the sawmill is operating at that pace.
Mikolajczyk took the inquest through a series of mechanisms used to deal with sparks that may get into the dust collection system. They include water injection, abort gates that shut the system down and, if the sparks reach the baghouse, blowout panels to allow the blast to dissipate away from the mill.
In response to concerns about dust building up inside the cabinets, motor control centres - where workers shut down machinery before they start working on them - are housed in separate rooms that include double doors and positive pressure.
Many of the motors out in the sawmill are now rated for use in high-dust areas, Mikolajczyk said.
Windows in the lunchroom and administration officers have fire-rated shutters, each work station has at least two exit routes and escape route maps are posted at each location. And the main first aid room is located outside the sawmill, as is the compressor room and the power distribution centre.
Rather than sucking air up and out through the roof, the facility's ventilation system takes air in from the top and forces it downwards where it escapes through the lower sections.
"The mill creates most of its dust and handles all of its waste in its basement so we thought 'why would we want to draw the air over that and pull it up to the ceiling?'" Mikolajczyk said.
If a fire breaks out, the ventilation system automatically shuts down to reduce the supply of oxygen.
In answer to concerns about methane on the site - it was once a landfill - a methane mitigation system is in place. It's a series of pipes running underneath the mill's foundation and connected to wells outside the mill.
If the methane level reaches 50 per cent of acceptable standard, alarms go off and the mill is evacuated.
Asked what older sawmills should focus on when retrofitting to prevent a disaster on the scale of Lakeland, Mikolajczyk emphasized using properly-rated motors, installing shedder plates and putting in a vacuum system.
The new sawmill has been operating since December.
