Students self-isolating in halls of residence were ordered to wait in their room if there was a fire so others could leave first.
The instruction – sent out in an email this week – has now been changed after North Yorkshire Fire and Rescue Service contacted the university to point out it risked lives.
It is understood the service was contacted by concerned students worried that holding back while flames raged through the building was not safe.
The initial email told recipients that the new rules had been drawn up to ensure non-isolating residents did not catch Covid-19 during an evacuation.
It said: “If you are self-isolating and the fire system in your accommodation building is activated please follow these procedures to ensure your safety.
"When the alarm sounds; stay in your room for one minute then make your way to the nearest refuge (this will allow non-isolating individuals to exit the building)."
But the university said on Friday that the advice had now been “updated and changed” after local fire chiefs had been in touch.
A spokesperson told BBC Yorkshire: “We take the health and safety of our students and staff extremely seriously.
"All students are required to undertake a mandatory fire safety induction and this clearly states that all students should evacuate the building immediately, meeting at the designated fire assembly point.
"Students are reminded that in gathering at the fire assembly point, they should adhere to social distancing guidelines."