1-3 Professional advice

 
The sinks and drains in the laboratory are fitted with “drain traps.”
Just like a household sink, the drain trap has a certain amount of drainage to prevent the sewage side odor from entering the room.
 
This is called “suifu” (a water seal).
 
If you do not use the sinks or other equipment. for a long time, the water in the trap may evaporate, and the water seal may become ineffective.
 
In such a case, if you let water flow for a while, the smell will eventually dissipate.
 
Another possibility is that the room is in an extreme negative pressure state.
 
In the case where there is an imbalance in air supply/exhaust balance in a relatively airtight room which leads to an extreme negative pressure, in such rare cases, the negative pressure exceeds the height of the water seal, causing the odor of the sewage to be sucked into the room.
 

1-3 Advice for Initial support/correspondence 

 
If the smell is coming from the vicinity of a water drain, identify the drain involved. (identify the source)
If the smell is coming from the vicinity of a water drain, determine the source and identify the drain involved.
 
Once you identify the source, check first the condition of the drain. Check to see if there are any unexpected incidents such as chemical spills.
 
If there is seems to be no particular problem in the drain, run water for a while so that water accumulates in the drain trap. Then, observe the changes.
 
If the room is under extreme negative pressure, there will be a wind noise at the entrance.
 
In that case please refer to the following.