Smoke stack

The Smoke Stack Intake starts this build and is the only block of it you connect a pipe to. Why a furnace needs a stack, and where it sits in the gas network, is on Hot blast.

Layers +2 to +10 (the same course)

#	Colour	Name	Matches
1		Smoke Stack Intake	smex:smokestack-intake*
2		any Refractory bricks	game:refractorybricks-good-tier*
3		Empty (air)	game:air
4		any bricks	@(claybricks-(good-fire|clinkerrough)|refractorybricks-good-.*|brickcourse-.*)

Every block is drawn in its default orientation: the layout carries no facing data, so the build order below names the facings.

Materials

Block	Cells
Smoke Stack Intake	1
any Refractory bricks	24
any bricks	36

The shape of it

The stack is a squat three by three base with a single-cell flue running up out of it, twelve levels in all. The Smoke Stack Intake is the control block and sits at the bottom of the front face, at ground level, with one level of base below it.

• The base is three levels of refractory brick, three by three. The bottom level is solid; from the intake's level up, the centre cell of each course, one cell behind the intake, is left open as the bottom of the flue.
• The chimney above it is nine more levels: four brick cells around one open cell, straight up. Any ordinary brick does for these, fire clay, clinker or a brick course of any colour.

Build order

1. Find a spot with twelve clear levels and a pipe route back to the furnace's exhaust main. A roof or an overhang inside those twelve levels blocks the build; nothing above them is checked.
2. Place the intake facing the way the pipe will arrive; it is the control block.
3. Hold ctrl and shift and right-click it for the build outline and the chat list of what is still missing.
4. Build the refractory base, then the chimney course by course, leaving the middle cell of each course open.
5. The intake reports "Smoke Stack structure is complete!" when it is done, and it starts venting whatever the network gives it.

Running it

The stack is the safety valve of the whole gas side, and it is the reason a furnace keeps melting while its stoves change over. It pulls 96 L/s off the network it is connected to and throws it away, which is more than one blast furnace makes at full melt rate.

1. Pipe it to the same exhaust network the furnace and the stoves are on. It only draws from a run whose pipe faces back at the intake.
2. Put a pressure-relief valve in the branch that leads to it, so the stack takes the surplus and the stoves take the rest. A fresh valve gates at 1.0 atm, which is under the 2.0 atm the furnace pushes its exhaust to, so it opens under load.
3. Look at the intake to see what it is actually clearing: Consuming 96.0 L of Gas when the run has that much in it, less when it has not. The figure is what the stack took on the last tick.

Smoke rises from it while it is venting, sooty for exhaust and pale for steam. A stack passing plain air shows nothing, which is not a fault.

What goes wrong

The furnace chokes anyway. The stack is on a network the furnace's flue cannot reach, or the branch to it has no open path. A furnace with nowhere to put its exhaust stops melting and says "Exhaust network is full! Production halted."

It vents nothing. The intake's connector face is not looking at a pipe, or the run it is on holds no gas.

A stove swap puts the furnace out. The overflow branch was built after the fact. It has to exist before the first swap; see Hot blast.

The build will not complete near the top. A snow layer is not air, and neither is a vine or a torch. Clear the column.