Refer to https://wiki.factorio.com/Pollution for source.

Final pollution value is (pollution multiplier * energy usage multiplier * base pollution)

Lets take the Furnace Warehouse as an example.

An electric furnace has 0.9 pollution at full power - 0.005/KW.
Furnace Warehouse has 36225 pollution at full power - 0.805/KW.
(Simple formula of pollution value / KW)

That's 161x as much pollution as an electric furnace, while being only 10x as fast. I assume the energy cost is intentional as well as the recipe being inefficient (10x electric furnace speed while costing 20).

This isn't the only building out there doing this by the way. It also almost entirely nullifies air scrubbers (Both yours and other mods) I suggest you make a full pass on all buildings that produce pollution.

0.17.7 changed the values. Using the example above:

Furnace Warehouse: 4500 pollution / 45000 KW = 0.1 pollution per KW
Electric Furnace: 0.9 pollution / 180 KW = 0.005 pollution per KW

0.1 / 0.005 =
20x the pollution generation of a furnace per KW
40x the pollution generation of a furnace per crafting speed

This - in addition to the nerf to productivity module pollution generation and buffs to air scrubbers - looks a lot better than previously. Thank you for taking the feedback in mind!

0.17.7 changed the values. Using the example above:

Furnace Warehouse: 4500 pollution / 45000 KW = 0.1 pollution per KW
Electric Furnace: 0.9 pollution / 180 KW = 0.005 pollution per KW

0.1 / 0.005 =
20x the pollution generation of a furnace per KW
40x the pollution generation of a furnace per crafting speed

This - in addition to the nerf to productivity module pollution generation and buffs to air scrubbers - looks a lot better than previously. Thank you for taking the feedback in mind!

Thank you for giving it! Pollution levels have always been a kinda iffy thing so feedback for it helps alot.