Electronic cigarettes have been outlawed on all buses.
The news will come as a breath of fresh air for commuters on Dublin Bus and Bus Eireann, as both companies have extended their policy on tobacco smoking to include the prohibition of e-cigarettes and smoking vapour devices.
Under Bus Eireann's new rules, all smoking, including the use of cigarette substitutes, is banned on buses and coaches and in all parts of bus stations excluding designated smoking areas.
Dublin Bus has implemented a similar policy. A spokesperson for the company said the anti-smoking policy was "a very positive thing."
They added: "Anything that might cause confusion to the policy, like an e-cigarette, would be unhelpful."
The news that Irish buses are now e-smoke-free comes in the wake of Irish Rail's announcement that it would be banning the use of all such devices.
The company said the decision to prohibit all "faux-cigarettes" was prompted by a high volume of feedback from customers.
Irish Rail said that the use of e-cigarettes may compromise the clean-air policy it had implemented after tobacco was banned in public places nationwide.
In a statement, Irish Rail said: "we worked hard after the introduction of the smoking ban to ensure no smoking occurred on our services or in enclosed areas within stations, and we have an almost 100pc compliance on this."
The company also said it considered the policies of other railway operators across Europe and found that the majority of them had an anti e-cigarette policy.
Details of the ban can be found on the Irish Rail website.