Rotton Egg Smell

[honky-tonk]

Can anyone help we are having bad smells in conservatory and dining room these rooms are near to a drain storm and main sewerage man hole. Drains have been unblocked over 3 weeks ago and we have been experiencing these bad smells for the past 4 days
Thanks

[fairkatrina]

call the drainage company, they'll send someone round to have a look and see what's wrong. Sounds like it's backed up somewhere along the line.

[Docsteve]

The release of H2S gas (rotten egg smell) is due to organic material rotting in the absence of oxygen. You will need to kill the bacteria without releasing the gas, which is poisonous in large quantities. Our noses are pretty acute at sensing even small amounts so don't worry. The recent work will have brought a lot of this material to the surface and perhaps time and aeration will cure this.
I would favour a reducing chemical to kill the bacteria and break down the organic sludge - for example a large amount of bleach. Conventional drain cleaners use sodium hydroxide or sulphuric acid and can fail catastrophically with the combination you have. In fact, people have died of H2S poisoning/asphyxiation when using sulphuric acid in this situation.
This is a job for an expert - as a chemist I would throw the bleach down and then retreat - but I don't know your situation. Get a drain expert - but worry if they get out the suphuric acid!