Pneumatic tube pipe and sewage treatment plant: what they have in common

1. Step 1. Pneumatic tube pipe — is part of — Pneumatic tube. A network of tubes between stations.
2. Step 2. Pneumatic tube — has part — Compressor. A pressure or vacuum blower.
3. Step 3. Compressor — is part of — Sewage treatment plant. Blowers supply oxygen to the microbes.

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