Great point! So if you have a firework that sparks some dry grass or brush, your home fire extinguisher will likely be fine as long as the fire doesn’t get too big before you can grab it.
However, if you have a hoard of fireworks that catch fire, you’re better off running and calling the fire department than trying to quickly put that out with your home fire extinguisher as it likely won’t work.
It can be both, and in this case is. They put the foam bricks in place as an April fools joke to raise awareness and plan to leave them, but they don’t think the city will allow the foam bricks to stay.
https://www.cbc.ca/news/canada/british-columbia/granville-island-pedestrian-safety-crosswalk-1.7160751