The emergency purge is a useful feature for many situations, and can be very helpful in purging smoke from a fire in the hood. While it can fan the flames, this is not the root cause of your problem. The flexible connection would have melted sooner or later; the purge probably just sped up that process a little. Fume hoods should never be connected with flexible, nonfire-rated duct. It's best to hard duct everything with steel duct, but if you absolutely have to have a flex connection, they do make some flexible steel connections, they're just not as flexible as most non-steel ones. Regards, Stan
The emergency purge is a useful feature for many situations, and can be very helpful in purging smoke from a fire in the hood. While it can fan the flames, this is not the root cause of your problem. The flexible connection would have melted sooner or later; the purge probably just sped up that process a little. Fume hoods should never be connected with flexible, nonfire-rated duct. It's best to hard duct everything with steel duct, but if you absolutely have to have a flex connection, they do make some flexible steel connections, they're just not as flexible as most non-steel ones.Regards,
Stan