Ventilation for Sewage Lift Station

Duplicate thread.

Research "upblast exhaust fan" or similar terms. See the pictures that accompany this search.

2 points. there is almost certainly local code requirements /guidelines on venting H2S. find out or you might kill someone. second, general rule o ventilation...you can't take it out if you don't put it in first. so if you want to move 100cfm you must provide a 100 first or you'll just be drawing a vacuum and performing little work.

Wahajmech,

Often the drawings for the electrical controls will show a fan but not the pipe or duct since those are on the drawings for the mechanical or structural components. There needs to be a pipe or other vent path from the lift station to the exterior, as well as sufficient open area to allow replacement air to come in without being contaminated by the air being exhausted (from a different side of the structure as an example). If you don't have a working blower with exhaust piping, you can put a temporary flexible hose on an external fan to ventilate this station.

Once the vent has been established and has run for a few minutes, you should verify the safety of the air in the lift station with a suitable gas monitor that will confirm an adequate O₂ concentration and concentrations of CH₄ and H₂S that are well below the lower permissible levels. Only then can you enter the station. Also, know and follow any other requirements for "confined space entry" that apply to your location. I know that for decades the monitoring was usually ignored by most people, but your life is more important.

--JMM

The American Society of Civil Engineers (ASCE) have minimum design standards in one of their handbooks. You need to purchase it.

Sizing of exhaust blowers for both the wet well and the dry well, as well as a gooseneck exhaust pipe/vent, are sized relative to the volume of both pits. And both pits need to be ventilated separately.

It is absolutely imperative to have a on-off switch attached to the access doors (in the roof), for life safety issues, that automatically turn on the exhaust blowers when the doors are opened.

You must test the inside air for obnoxious gases present inside either pit before entering. Since either pit is a "confined space" it is imperative that workers have received OSHA Confined Space safety training.

That's just for starters!!!

Thanks Capt Moosie, for the good advice. Where were you when I was down in that lift station replacing check valves? We did have a window fan blowing down there, I think.

I probably was on vacation then!

Stay safe!

By the way, you should realize that pure methane (CH4) is odorless. What you were smelling was a little hydogen sulfide (H2S), and/or rotting organic matter and/or algae.

First, H2S and CH4 are significantly different, even though frequently encountered in the same sorts of places.

H2S is a skin and/or eye irritant at only 12-15-ish parts per million by volume (ppm/v). Prolonged exposure to higher concentrations is increasingly toxic, up to and including loss of consciousness, and death...

Methane, on the other hand, is also quite hazardous via a different mechanism. It can be ignited by a spark from any source, but only if at a concentration in excess of about 50,000 ppm/v , which is its' Lower Explosive Limit (LEL). It also has an Upper Explosive Limit (UEL) of about 150,000 ppm/v, but that does not make it safe.

If, for any reason and/or sequence of circumstances, accummulated methane is combined with enough oxygen, and the right spark, the result will be veeeeery explosive, as happened in the Fairfax Area of Los Angeles, some 20 years ago... That accident has lead to a growing national awareness of methane hazard, and more stringent Code requirements, as well.

In any case, find out what the minimum ventilation requirements are in your jurisdiction, and then double it, while you still can...

''Bingle'' it and see what you can find.

The light switches and switch-gear used should be ex-proof and no smoking allowed inside.