The National Bus and Rail Union (NBRU) has called on the Government to reintroduce the mandatory wearing of masks on public transport.
NBRU General Secretary Dermot O'Leary said it was time for the Government to reintroduce the measure for a limited period of time, as the HSE faces significant pressure from a surge of Covid-19 and other respiratory viruses.
Speaking on RTÉ's Morning Ireland, he said: "There are concerns among public transport workers, particularly those exposed on a daily basis.
"There is potential here for Government to reset over the Christmas period, where there will be an obvious lull in the numbers travelling, and that is the time we believe for Government to reintroduce mandatory [mask-wearing] for a limited time," Mr O'Leary said.
With people around the country travelling home for Christmas, he added that it is "a bit late for that mandatory requirement in advance of Christmas to put that mandatory requirement in place".
Customers have been asked to leave windows open on public transport to help with air circulation and ventilation.
Earlier this week, Chief Medical Officer Professor Breda Smyth warned that Ireland is "in the eye of a respiratory virus storm as we enter the Christmas period".
The HSE's Chief Clinical Officer Dr Colm Henry advised that as well as public transport, people should wear masks in "any setting where there is any degree of congestion and where they are in the company of an older person".
Also speaking in RTÉ's Morning Ireland, Eleanor Farrell, Bus Éireann's Chief Commercial Officer said that passengers are advised to wear face coverings.
She said the majority of town and city services "have windows that can be opened and we do recommend that they remain open during the period where possible."
Services with windows that cannot be opened are equipped with air conditioning that works to a very high standard, she added.
Iarnród Éireann is reminding rail users of the advisory that is currently in place on mask wearing, Barry Kenny, Iarnród Éireann Corporate Communications Manager has said.
He added that only about one quarter of trains have openable windows and the remainder have air conditioning systems which refresh air every eight minutes.
