Definition
The safety distance is the minimum separation between a firework at the moment it functions and the audience, buildings or any unprotected person. For consumer categories it is set by standard EN 15947 and printed on the label: 1 m for F1, 8 m for F2, 15 m for F3. For F4 fireworks and T2 articles the manufacturer's instructions apply, and the display supervisor adapts them to the site and the weather. In French professional practice the working rule for a shell is roughly one metre per millimetre of calibre (a 100 mm shell requires 100 m), extended downwind. CERFA form 14098 requires a site layout on which these distances are drawn explicitly.
In practice, for the display company
It is the first constraint of a site survey: it decides the largest calibre you can fire at a given venue, and therefore the quote. PyroDesk works out the required distance from each product's calibre in the firing plan, flags fireworks incompatible with the recorded site and carries the distances onto the layout attached to the pre-filled CERFA.