Are glass lids safe?

Yes and they allow you to monitor the cooking without lifting the lid. The glass is toughened, like a car windscreen, but in extreme circumstances can break. Glass lids are also suitable for use in the oven. Care should be taken with hot lids as subjecting them to sudden changes in temperature, such as placing the hot lid in cool or cold water, can make the lid shatter. Replacement lids are available to purchase, or in the rare circumstance that there has been a fault can be replaced by Customer Service.