Gas Filter
Output: Filtered Gas Output
Other Gas Output
Red: Disable
Gas Filter sieves the selected Gas packets out of mixed input, sending them into a separate pipe.
Usage
Gas Filter has 2 outputs, the standard green output and another orange output in the center. The orange output is for the gas that was selected to be filtered out, and the green is for all the other gases that come through the filter. For example, using a Gas Pump, you may send the mixture of gases produced by an Electrolyzer into the gas filter and send Hydrogen to a separate pipe for use in a Hydrogen Generator.
It only draws Power while it is in use (that is, has gas flowing through it). This means it is optimal to sort out the expected gasses first. For example: an air filtration system that primally finds oxygen with CO2 and polluted oxygen sometimes should have an oxygen Gas Filter first and then the second most common gas then the third. Note: you can work out how common a given gas is by pumping gasses from the area into Gas Reservoir until full then looking at the contents.
Mid/Late game alternatives
A better alternative become available once you have access to Refined Metal and have unlocked the following research: Automatic Control, HVAC and Improved Ventilation.
As you get further into the game power becomes increasingly important to conserve, often a base at this stage will have quite a few gas filters that are each draining 120W while in use this creates a noticeable drain on the system. A solution to this is to replace gas filters with the setup #1, this will check if a gas incoming from the left is a particular gas and if so turn off the shutoff filtering it. This setup only requires 10W per filter, a massive improvement.
Limitations
Whilst the above system is cheaper it has an important limitation to be aware of:
- If power is lost the filter will start passing gas without filtering it, rather than stop passing gas completely as the Gas filter would.
- There is a chance that the filter will not work correctly if the pipe is backed up (full). Because the detection happens before the gas gets filtered, the automation may activate with the correct gas sitting on the element sensor, allowing the wrong gas behind it to pass through.
To solve the power loss issue you can add a Smart Battery (Requiring Generic Sensors) set to: Standby 40%, Active 20% connected to a not gate connected to a Gas Shutoff at the start of the filter mechanism, this will then prevent the filter from trying to filter if there is insufficient power to do so. As shown to the right (#2). If this new design is used then 2 things also become considerations: The filter now takes up significant space and, the whole design now costs 20W per sort. In response to the first concern unless space is very low the power saved is normally worth more than the lost space as and as for the second, this problem can be mitigated by putting multiple filters next to each other (as only one power cut off is required for the whole system) and regardless it is better than using actual gas filters.
To solve the backed up pipe issue you can let the backed up pipe run through a gas reservoir and connect it to the main shutoff valve with the Smart Battery through an AND gate.
Overall this is normally a good improvement on the gas filter for most players.
There is also an earlier, more rudimentary gas filter using only bridges and a gas valve, with the advantage of never under any circumstance outputting the wrong gas. The downside is that it is more voluminous and must be primed with an initial packet of the gas being filtered.
