в котором поддерживается температура
• The mixture was heated in an oven held at a temperature of 170°C (or where a temperature of 170°C was maintained).
Русско-английский научно-технический словарь• The mixture was heated in an oven held at a temperature of 170°C (or where a temperature of 170°C was maintained).
Русско-английский научно-технический словарь