In response to Jim then there's a limit to the reverse engineering carried out as part of the FRA- for example I do not expect anyone to carry out CFD modelling, simply to recognise that travel distances are excessive by benchmark standards, that there clearly must have been a fire engineered solution to justify this, and to evaluate in the absence of information and using a combination of training, knowledge and experience to whether the original solution, in the absence of information is likely to require review. I agree you have to accept that even if wrong, if it has been approved by building control and the fire service all you can do is summarise your concerns and recommend a review as an action in the risk assessment.
But I would expect a competent assessor for example to:
For sprinkler systems evaluate whether the category of goods, mode of storage and height of storage is in accordance with the design and capacity of the system
For fire engineered solutions to assess whether travel distances and risk levels are in accordance with the approved design or if no details available use trading, skills and knowledge evaluate to whether travel distances are still likely to be in accordance with the original design- many warehouses for example have been converted from open plan block storage to palletised rack storage thus increasing travel distances and reducing visibility. Many with roof smoke vents have had large mezzanine floors installed. Many smoke vents conflict with sprinkler design.
For flats with extended travel distances and mechanical ventilation (which is nowadays dual purpose for ambient ventilation in which all vents may be open simultaneously on a hot day) whether the design parameters are in accordance with BRE or similar guidance and whether it is correctly configured (one scheme I came across with 45m dead ends had a fire engineered solution approved by all parties with doors not open for the prescribed periods, smaller design fire and modelling with thresholds taped but nobody noticed).
And a brand new chilled warehouse in which the fire engineers had shown their full calcs and illustrated the smoke vents on the drawings. Trouble was no vents had been installed at all and all parties had mistaken the chiller cold air inlet vents as being smoke extraction vents!
I could go on with many more examples but have no doubt bored you all enough!