1. Ducted chimneys are generally recommended whenever possible. The primary reason is that they physically remove the smoke and fumes from the kitchen, preventing them from recirculating. This system is considered more effective and healthier, as the extracted smoke is directed entirely out of the kitchen area. Ductless chimneys are only suggested as a last resort for kitchens that cannot be fitted with ducting.

1. Ductless chimneys should be considered when it is impossible to install a duct due to layout limitations, such as when there is no external wall or vent access. For instance, if the only viable place for a chimney is on a wall without an outlet to the outside, ductless is sometimes considered the only option. However, even in these cases, combining a ductless chimney with an exhaust fan pointed towards the ceiling is recommended, to help to remove the air.

1. Ducted chimneys generally require less frequent maintenance. A deep clean every year or so is often sufficient, especially if the chimney has an auto-clean function. Ductless chimneys, however, demand more regular attention. They rely on charcoal filters that need to be replaced every 6 months, which incurs ongoing expense.

1. Initially, a ductless chimney might seem cheaper. However, when factoring in the costs of repeatedly replacing charcoal filters, ductless chimneys can become more expensive over time. Ducted chimneys may have a higher upfront cost, but they are generally cheaper to maintain long term because they don't rely on filters that need regular replacement. The lifespan of ducted systems also tends to be longer than ductless.

1. No, a ductless chimney does not eliminate smoke. It only filters the smoke to remove some of the particles and odours before releasing it back into the kitchen. Therefore, smoke still remains present in the kitchen area to some degree. This is one of the key reasons why ducted chimneys are preferred whenever possible - because they completely remove smoke from the kitchen.

1. Ducted chimney installations can be more complex if the external wall is far from the chimney or if the duct has many twists and turns. Conversely, ductless chimneys are easier to install because they don't require any external ducting and are simply mounted to the wall. However, the speaker points out that the additional effort involved in fitting ducted systems is generally worthwhile given that ducted systems work much better.

The primary recommendation is to install a ducted chimney whenever possible. Ducted chimneys are better in terms of functionality, performance, and cost-effectiveness over the longer term. Ductless chimneys should be considered a last resort only when a ducted system is truly impossible due to space or installation constraints. The general advice is: if you have an outdoor exit point in your kitchen, choose a ducted chimney every time.