I have sewer gas smell coming from the stand pipe in my laundry room is it OK to block the top of that opening i.e. insulation duct tape etc.

Is there a trap or a elbo at the base of the stand pipe. Cover the pipe with duct tape until I can get back to you. Regards, Tom

We bought the house new Im an electrician so I was here during construction I do remember there being a trap on that stand pipe.Thanks for such a quick response.

Now, stick a rod or broom stick down the stand pipe. It should come back with at least a ionch and a half with liquid on the bottom. If the stick come back with water on it flush a upstairs toilet and listen at the stand pipe for any bubbling noises. Let me know, Tom

There is water in the trap but really not sure how much and there is no bubbling sound when I flush the toilet up stairs..?.

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There is water in the trap but really not sure how much

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Go back and check. Several things could be happening.
1) The trap seal could be lowered by suction from a blocked vent**OR**
2) Fiber caught down in the trap could set up a capillary action that could lower the trap seal.
A lowered trap seal could allow sewer gas to escape into your house. If the water level in the trap is low that might just be your problem. Let me know, Tom