Originally Posted by WASBLR

Among all recent incidents of opening the emergency exit to 'get some fresh air' or such, it's been adults.

Originally Posted by AA

Qualifications

Customers must be advised that government regulations prohibit seating passengers in designated exit seat, on any commercial flight, when they answer NO to the following question. "The government requires any passengers seated in the exit seat be 15 years of age or older, be willing to assist in an evacuation and have no physical impairments that would prohibit your assistance. Airport personnel will make the final determination. Do you meet this criteria?"

Originally Posted by DL

Passenger Qualifications

When assigning an exit seat:

They must be able to comprehend instructions for operating the emergency exit including locating and operating a window exit or exit door and directing others to the exit
They must not be under 15 years of age and must not have a condition that might cause them harm if called upon to open an exit
They must be physically able to open an exit door and to lift and stow a 31-52 pound window exit
They must not require the use of a seat belt extension (this limitation is intended to preclude the hazard of entanglement with the additional length of the extension by those passengers attempting to expeditiously exit the aircraft)
Exit-row passengers must be willing to perform these tasks if instructed to do so.

Originally Posted by BA

Civil Aviation Authority requirements
In accordance with CAA requirements, the following categories of passengers cannot be allocated an exit row seat:

Passengers who are either substantially blind or substantially deaf, to the extent that they might not readily assimilate printed or verbal instructions given.
Passengers who are unable to understand and carry out instructions given in English.
Passengers who are unable to reach, open, lift and throw out the exit door in an emergency.
Passengers who because of physical stature, age or sickness have difficulty in moving quickly.
Children under 16 (whether accompanied or not) and infants.
Passengers who are travelling with anyone who would require their assistance in the event of an emergency.
When requesting an exit row seat you will be asked to verify your eligibility.