I don't have the ArtScroll weekday Siddur in front of me, now, but essentially, it said that one does not say Tachanun in a shul where a Brit will occur during that day.
If a Brit occurs anywhere in the shul building at any time during that day, and if the Brit is performed by anyone whatsoever, even an outsider who is renting a room for the Brit later in the day, does no one in the morning minyan say Tachanun? Is this how the halacha works, or is Tachanun omitted only if one of the people involved in the Brit (father, mohel, Sandak, etc.) is actually davening with the minyan?