If pyrotechnics have to be used in the film being made, the production company must first clear that matter with the film contact. That is not all however.
The production company must conduct risk assessment to see what using the pyrotechnics will entail. The production company should also provide a method statement.
The police, local residents, and businesses must also be informed if pyrotechnics are about to be used.
Atmospheric effects such as rain and snow have often been used to accentuate the emotions conveyed in movie scenes. They are effectively used in storytelling tools.
They can still be used by directors in London, but they must first be allowed by the film contact. The film contact will evaluate the weather forecast before deciding whether or not to allow the usage of the atmospheric effects.
Clean-up considerations are factored into the evaluation process as well.