In regards to COVID-19 when libraries do reopen, (and allow people in) is it advisable to ask customers to leave the public building if they are exhibiting any visible COVID symptoms? If so, are there benchmarks for how extreme symptoms should be or how policies should be worded? There are of course patron behavior policies in place allowing for the removal of anything disruptive, which can include noise or inappropriate behavior. There are some members of our leadership team who believe our safety reopening plan should include provision specifically mentioning symptoms of COVID-19 and the staff's/ library's right to remove them if symptoms are exhibited. There are other concerns that library staff are not medical professionals and we are not able to determine if a few sneezes and coughs are common colds, allergies or COVID. Attached is our library's current reopening plan.
As the member writes, it is very difficult to determine if some physical factors—coughing, a flush, seeming malaise—are in fact symptoms of COVID-19. Confronting a patron with suspected symptoms can also lead to concerns impacting community relations, privacy, and the ADA.
A good Safety Plan addresses this concern, without requiring patrons to be removed mid-visit from the library.
To position libraries to address the impact of patrons with suspected symptoms, New York's "Interim Guidance for Essential and Phase II Retail" (issued July 1, 2020) states:
CDC guidelines on “Cleaning and Disinfecting Your Facility” if someone is suspected or confirmed to have COVID-19 are as follows:
[emphasis on "suspected" has been added]
In other words: your Safety Plan, as informed by the most recent guidelines, should leave nothing to chance. By using this procedure, library staff are never put in the position of having to guess, ask, or consider if a patron's coughing, sneezing, or other behaviors are COVID-19...rather, the moment the possibility is "suspected," the Plan kicks into action.
Of course, if a patron is properly masked, some of the risk of exposure is limited, even if they are infected (this is why we wear masks and identify areas with six feet of clearance in the first place). And if a patron removes their mask mid-visit, refuses to keep appropriate distance, or refuses to spray down equipment after using it, THAT person can be asked to leave, simply as a matter of policy—whether they are exhibiting symptoms, or not.
So to answer the question: no, it is not advisable to ask patrons to leave the public building if they are exhibiting any visible COVID symptoms, for exactly the reasons the member provides. Rather, it is required that your Safety Plan keep people distant from each other, and that the library be ready to address any real or suspected exposure as quickly and effectively as possible.
That said, having signage that reads "Safety first! Patrons who are concerned about transmission of germs can arrange curbside service by [INSERT]" is a great way to remind people that if they are having an "off" day, there are many ways to access the services of your library.
I wish you a strong and steady re-opening.
 This answer does not apply to employees and visitors like contractors, who must be screened.
 Found as of July 25th, 2020 at https://www.governor.ny.gov/sites/governor.ny.gov/files/atoms/files/RetailMasterGuidance.pdf
 Found as of July 25th, 2020 at https://coronavirus.health.ny.gov/system/files/documents/2020/06/doh_covid19_publicprivateemployeereturntowork_053120.pdf
 I note that the DOH's "Interim Guidelines" do not include guidance to staff with suspected (as opposed to confirmed) exposure. If an employee feels they were exposed to a suspected case of COVID-19, however, that will impact their answers on their next daily screening, which will trip consideration of whether they can report to work.
 Or whatever other safety measures a library has identified. It is inspiring to read the variety of tactics out there, as listed at https://www.nyla.org/covid-19-library-reopening-plan-database/?menukey=nyla.
 Of course, if a patron is having a medical event and you have an immediate concern for their well-being, call 911.