Around 30 people had come to observe the panel's discussions on plans for Leeds Bradford Airport to rebuild its terminal, at Leeds Civic Hall today.
But once discussion on the item began, several members of the audience began coughing loudly before some took turns to speak out on environmental issues.
One began "Does Leeds City Council know that we have an emergency?
"Urgent and unprecedented actions are needed."
Three people then fell to the floor, before lying still for a number of minutes.
Chair of the committee Coun Jim McKenna said: "This is interrupting our meeting, can security act please?"
Security then ushered the speaker towards the exit, but other members of the audience then started speaking.
Coun McKenna then informed the room that the police had been called, before councillors left the room.
The meeting was reconvened around 20 minutes later.