"I do; well, not a better idea, a complimentary one. Have you heard of sodium azide?" Dumbledore shook his head. "It's a muggle explosive, they use it in the emergency cushions in their cars. With a bit of magic, we can make it a fine enough powder to hang in the air; you remember Grindelwald's experiments with thermobaric weapons."
"I do, but what if he uses a light spell instead of fire to get through the Devil's Snare? I suppose we could include a magical proximity detonator."
Flamel shook his head. "He would notice the magic and it would put him on guard, better that he not realize anything. Besides, sodium azide has one other advantage over Grindelwald's coal bombs."
Hm, so they've got an adult mandrake set to scream when the light comes on. And I need a bright light to repel the Devil's Snare. I could use fire instead, but that's probably what they expect me to use; they figure I wouldn't be willing to deafen myself even temporarily. Here goes.
After quickly pointing his wand at his head and deafening himself, Quirrel levitated the large dog off the trapdoor, opened it, and jumped down. A moment later, the large, carnivorous plant caught him. Pointing his wand where he guessed the main body of the plant was, he incanted "lumos solem". The plant swiftly drew back from him, letting him fall the rest of the way to the floor. In the wandlight, he could barely see the haze of fog hanging in the air. Huh, good thing I didn't use fire, I bet that fog is combustible. Nice try dumbldork. In the corner, he spotted the mandrake, loose from its pot and screaming. Not wanting to risk a spark, he walked over to the plant and stepped on it, he did not notice he was moving sluggishly. Then he released the spell deafening him, and paused a moment to listen. That's that... what was I doing again? Oh, stone. He took two steps toward the door, then paused. He was feeling dizzy and his wand light was fading. He paused a moment, when his master spoke. "Fool! That fog is poisonous! Quickly, protect yourself!" He let the lumos spell collapse and quickly tried casting a bubblehead charm. On his second attempt a small bubble of clean air appeared over his face. Still lightheaded, he fumbled in the dark to find the bezoar he kept in his pocket, found it, and ate it. Nice try, but a magic poison that slow is not a serious threat. Immediately, he felt a little better. Of course, bezoars are most effective against magical, ingested poisons. Once he was sure the bubblehead charm would hold, he re-lit his wand, which flickered dimly. That's odd, that poison must have been more potent than I thought. I'd better get out of this cloud and rest a minute to give the bezoar more time to work. With that goal in mind, he stumbled through the door and closed it behind himself. Seeing that he had left the cloud behind, and being too exhausted to maintain the charm, he let the bubblehead drop. In a minute, I'll be feeling better and continue, I'll just rest here a moment.
By the time he had used the bezoar, a significant portion of his red blood cells were already permanently destroyed; and, while the bezoar and the bubblehead charm protected him from what he would have continued to inhale, it did nothing to stop the sodium azide absorbing through his skin. He sat down and closed his eyes, intending to get up in just a moment. He was still there hours later when Dumbledore came to investigate. Tom Riddle's shade had already departed.