1.   Another is a missing or improperly installed vent line that is supposed to connect each fixture to the main vent stack.

2.   If other drains are stopped up or slow running, the problem may be in the main vent stack or a large drain line.

3.   One entire floor is equipped with wet labs, reinforced floors and vent stacks for early-stage life sciences companies.

4.   Problem areas include the spaces around plumbing vent stacks, holes for electrical conduits, chases around chimneys, gaps around ductwork and the open tops of interior partitions.

5.   The chimney and plumbing, including the vent stack, as well as the water pipes, should also be connected to the system.

6.   The vent stacks cannot be seen from the highway, and ethanol gas is invisible, so there is no cloud or haze hanging over the plant.

7.   Wiring, plumbing, vent stacks, air ducts and the chimney typically have holes or gaps that should be sealed.