College students will have to wear face coverings during lectures if they are sitting between one and two metres apart, under updated guidance.
If two-metre separation between students is not possible - and it won't be in many lecture halls - it will be a case of 'one metre with a mask'.
One source said that while the wearing of face coverings by students would not be mandatory where a two-metre distance could not be maintained, it would be "strongly encouraged".
The number of students in a lecture hall at any one time will be 50, under the Government's current Covid-19 rules.
College lectures are regarded as having the same status as any indoor public event, which are capped at 50 people at the moment.
The new guidance comes as another 50 cases of Covid-19 were confirmed yesterday.
However the Health Protection Surveillance Centre (HPSC) said no new deaths have been reported.
There have now been a total of 1,763 Covid-19 related deaths in Ireland.
Dr Ronan Glynn, acting chief medical officer, said: "I know the decision yesterday not to move to phase four will have been disappointing for many."
But he said that the priority for the National Public Health Emergency Team (Nphet) must be to control the spread of the virus in our communities and to protect the progress that has been achieved.
The wearing of facemasks in shops and shopping centres will be mandatory from Monday.
A Department of Health spokesperson said they expect there will be "very little need" for policing due to previous widespread adherence to public health advice and regulations.
However, she added that "as a very last port of call the gardaí can be called for issues regarding non-compliance".
The new detail of face masks for college students is set out in the 'Implementation Guidelines for Public Health Measures in Higher Education Institutions' to be published by Higher Education Minister Simon Harris today. It builds on a previous document.
Its publication follows consultations involving the Irish Universities Association, the institutes of technology represented by THEA, TU Dublin and staff union representatives under the aegis of the Irish Congress of Trade Unions.
The measures have been drawn up by senior public health experts within the higher education sector and endorsed by the HPSC.
Social distancing was a key issue in the recent discussions and the new guidance is more specific and provides stronger protection than the language in the initial document two weeks ago.
It draws a distinction between the minimum separation to be maintained between staff and students and between students and fellow students, which will allay concerns expressed by some staff.
The new guidance says a physical distance of two metres should be maintained under all circumstances possible.
It states that it should be feasible to maintain a two-metre separation between members of staff, or between staff and students, under almost all circumstances.
It adds that there will be exceptional circumstances where this cannot be achieved and, in such situations, appropriate precautions - such as face coverings, visors or barriers - should be used.
The guidance also notes there will be circumstances under which teaching cannot be delivered while maintaining a two-metre distance between students. This will depend on the size of the lecture halls and the number of students in a class. In such circumstances, it says the distance between student seats or workstations may be reduced to (but not less than) one metre, with appropriate precautions to minimise the risk of viral transmission, and specific provision made for vulnerable students.
The guidance refers to the recommendation of Nphet that face coverings be used in indoor settings where adequate physical distance cannot be maintained - in this case that is taken to mean two metres.