This one might be a bit hard for some people, as it is hard to not let them die by flames or heat instead of the smoke. They will die this way as the smoke gets into said person's lungs, and chokes them out.

• • • • •

I hummed as I tired her to the metal pole, high above the fire that I had started to light. I watched as the black smoke started to rise, and I smiled. The girl started to wake up and I smiled, grinned more to say.
She looked at me, and a cough came from her, and she started yelling at me. "Hush, honey" I told my wife. She had wrongly had an affair, and this was payback.
I watched as the smoke started to cover her, and coughs started choking out her words. She kept coughing and I saw her chest heave as she tried to breath. I knew she couldn't survive for much longer. I waved at her before turning around "Bye honey, I think I'll go spend time with that worse you were with"