Past Perfect Continuous – When do we use it?

1. We use the past perfect continuous to describe an action that started in the past and continued up until another action in the past.

• The house had been burning for half an hour before the firefighters arrived.
• They had been discussing the problem for three hours before they finally decided.

2. We also use the past perfect continuous for an action finished in the past whose result was visible in the past.

• It had been snowing all night. (we could see the result)
• He had been working all night and was exhausted.