Internal fire rated window recommendations?

[Guest Sophie J]

Hello.

We are buying a second floor flat in a converted building. It has an unopenable window from the flat to the communal stairwell, and one from a storage room within the flat to the main corridor within the flat. 
 

We have had our survey done and the surveyor has flagged he thinks these windows might not be fire rated. 
 

I spoke to a reputable window company about getting a quote for fire rated replacement windows, and the owner wasn't sure what would constitute a fire rated window. 
 

Can anyone advise me: 

- what consists a fire rated window? Could you point me to a specific example?

- who should be able to assess whether these windows are fire rated?

- if they aren't fire rated, is there a particular type of company I should be seeking a quote from, rather than a normal window company?

Many thanks!

[AnthonyB]

This company can help https://www.checkmatefire.com/news/specifying-fire-resistant-glass