There are a number of potential causes for sewer odor inside your house. BE SAFE:
Turn off gas and propane sources and get out of the house immediately if there is any possibility of a leak. Do not stay in the house unless and until the problem is found and adequate measures have been taken to ensure your safety. After eliminating gas or propane leaks or any outside source (trash, manure, etc.) as the cause, there are several other possible sources to investigate. Check that the seal around your toilet is not broken. If it is, call a plumber to repair or replace the seal. Make sure there are no broken pipes in your crawl space or basement. Traps for sinks, bathtubs, toilets and drains should contain water. You may need to run several gallons of water down drains and toilets to refill the traps. If you have done any recent plumbing updates or changes, be certain that you have capped off the old lines. Check your vent pipe for obstructions such as bird nests, dead animals or debris. If you have a sump pump, check the basin for odor. If still unsure of the source, call a plumber or other professional as needed for assistance.