I'm replacing an electric cooktop with downdraft ventilation. Does building code require that I keep this ventilation, or can it be removed?
Because code varies by region, it's difficult to say yes or no to this.
Typically you only really need ventilation to the outside if you have a gas range. Often the hoods on top of electric cook tops just recirculate the air inside and don't actually vent outside. That being said, the often have a carbon filter which is handy for removing odors. They also usually have a light on them which is also handy for cooking.