Answer: The two complex sentences are:
Because general ventilation does not achieve the necessary control, we therefore recommend that all welding sites install extra fans and venting.
Since individual staff members will be initially responsible for their own safety, you should ensure that welders are suitably instructed and trained in the use of these controls.
Explanation:
When a sentence contains an independent clause and at least one dependent clause, we consider that sentence complex. An independent clause is a group of words that can stand on its own as a sentence. On the other hand, a dependent clause does not express a complete thought and cannot stand alone.
In the sentences listed above, the two complex sentences are the second and the last one. They both begin with a dependent clause that cannot stand on its own and is followed by an independent clause.
