Complex sentence: This particular model was used extensively is Laos during the Vietnam war, where, due unexploded canisters comprising up to 30% of fragments, there are an estimated 10 million unexploded cluster bombs.
Split into simpler sentences: This particular model was used extensively in Laos during the Vietnam war. Unexploded canisters comprising up to 30% of fragments may have an estimated 10 million unexploded cluster bombs.