Mossmorran operators have been told to deal with unacceptable impacts of flaring as soon as possible.
Environment agency Sepa served permit variations on both ExxonMobil Chemical Ltd and Shell UK requiring them to implement best available techniques in the shortest time frame possible.
Changes demanded will require significant investment but Sepa said they would make flaring, a necessary safety feature, an exception rather than routine.
People living near the site by Cowdenbeath have complained of severe disruption from flaring during a series of what are termed process upsets.
ExxonMobil, which operates Fife Ethylene Plant, was set a deadline of two months to produce a plan for new ground flare technology.
Shell was told to provide its plan for a totally enclosed ground flare system by the end of January 2020.
Installation of noise reducing flare tips are also required to be installed by ExxonMobil in 2020 and in 2021 for Shell, which runs Fife NGL Plant.
Ian Buchanan, of Sepa, said: “We’ve moved to vary the operating permits of both ExxonMobil Chemical and Shell to require them to take action in the shortest possible time frame.
“Addressing the unacceptable impacts will require substantial investments of which both companies are fully aware.
“People rightly expect that their lives won’t be impacted by nearby industrial processes.
“Most also recognise that addressing the root causes won’t happen overnight.
“We want and expect ExxonMobil Chemical to move faster.”
Jacob McAlister, ExxonMobil’s manager at Fife Ethylene Plant, said significant progress had already been made, with 12 steps prioritised to prevent the need to flare.
He said: “Our key process actions have already delivered benefits, as was demonstrated during our planned flaring event in July, when we significantly reduced the size of the flare itself and the length of time it was operating.
“Work on the planning process with Fife Council for our new advanced flare tip due for installation next year is also underway.
“This technology alone can reduce the noise and vibration compared with our current flare.”
Teresa Waddington, Shell’s Fife NGL Plant manager, said: “We have received a notice of permit variation and we will review it carefully.
“We are committed to operating the Shell Fife NGL plant within regulations, and improving in alignment with best available techniques for flaring practices.
“The plant plays a vital role in the supply of energy to Scotland and the UK every day, and we strive to minimise our impact on the local community.”
Sepa also published its latest air quality monitoring report which showed no breach of air quality standards.
Its regulatory investigation is expected to conclude by the end of November, including new lines of enquiry uncovered during the latest phase.
