What’s that smell?


That sewage smell is likely H2S. Put politely, it smells like rotten eggs. H2S gas occurs when waste builds up in sewer lines which can happen naturally over time, in areas that are used seasonally, or when population densities change. I.e. when that new apartment building at the end of the block gets finished…


Other things that can contribute to H2S buildup are:

  • High heat- the summer months definitely get smellier
  • Flat areas where the waste is ‘standing still’ and harder to pump through
  • Proximity to pump stations and wastewater plants
  • New subdivisions- New sewer line pipe sizes and grades are designed for ultimate flows, sometimes it takes years to achieve the designed flows

Is H2S dangerous?

The smell from H2S is irritating, but it’s also a warning as the gas can be incredibly dangerous and destructive if left unchecked. H2S stands for Hydrogen Sulfide, it is produced by bacterial breakdown of organic materials and human and animal wastes and can also be a byproduct of natural gas, hot springs, and crude oil.

The rotten egg smell that pesters neighborhoods is an indication of very low levels of H2S, between 0.1 and 5ppm (that’s parts per million). From 3-5ppm the odor gets stronger and can cause nausea, headaches, tearing of the eyes, and airway constriction. At 20ppm we can add dizziness, irritability, loss of memory, and loss of appetite to the list of symptoms. From 50-100ppm exposure for an hour can lead to conjunctivitis and respiratory tract irritation. Over 100ppm you’ll lose your sense of smell and after 15-30 minutes your breathing will alter and drowsiness will set in, over 48 hours of exposure at this level can lead to death. From 200-300ppm exposure over an hour can cause pulmonary edema (excess fluid in the lungs that makes it hard to breath). Levels from 500-700ppm leads to collapse in 5 minutes, serious damage to the eyes, and death after 30 minutes. 700-1000ppm will knock you out instantly and kill you in minutes and levels over 1000ppm cause instant death.


What do I do if I think I have an H2S problem?

If you smell H2S in your neighborhood you’ll want to contact your local wastewater plant, though it can be difficult to get in touch with the right person. If you want help we’re more than happy to provide it, just fill out the form below with a description of your problem and where the smell is occurring and we’ll get you in touch with the people that can help solve the problem.


PLEASE NOTE: H2S and Mercaptans (the artificial odor added to natural gas) can smell very similar. If you suspect a gas leak IMMEDIATELY EVACUATE the area and call 911 from someplace safe!