Final answer:
If you recognize someone choking at the farmers market, check the scene for safety and assess their ability to breathe or speak. Encourage coughing and perform the Heimlich maneuver if necessary. Call for emergency help if the person becomes unconscious or the maneuver doesn't work.
Step-by-step explanation:
If you recognize an 18-year-old choking at the farmers market, the first step you should take is to check the scene for safety. Ensure that there are no immediate hazards that could put you or the person in further danger. Once the scene is safe, you need to assess whether the person is able to breathe or speak. If they cannot, it means their airway is partially or completely blocked.
To help someone who is choking, first encourage them to cough forcefully to try and dislodge the obstructing object. If that doesn't work, you can perform the Heimlich maneuver on them. Stand behind the person, make a fist, and place it above their navel. Grab your fist with your other hand, and thrust inward and upward forcefully. Repeat this motion until the object is dislodged.
If the person becomes unconscious or the Heimlich maneuver doesn't work, you should call for emergency medical help immediately.