... It'll have to spend some time out in the shed first, it was in a house with smokers so it stinks to high heaven :/

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Time helps. But depending on the sensitivity of your nose, some smoker contaminated systems stink for years afterwards. There is some tar film everythere inside and out that cleans up well with ethanol wipedowns. But the worst area seems to be right around the cooling fan, where gross powdery deposits of tar and ash build up on the fan blades, and later shed onto downstream components and into the air. If you can access the blades, you can remove this ash buildup by cleaning in place with moist cotton swabs....much better than smelling and breathing it whenever you run the system!