G’flott’s Olfactory Nightmare

What's it called? G’flott’s Olfactory Nightmare (in short, GON)

What does it do? G'flott's is one of three very similar room spells (Sekiri called them in his site 'Pragi Clones'), the other two being Effermhor's Hypersonic Assault and Pragi's Fiery Gaze. All of them use a component and cause some damage on all the people in a room; also, the damage outputs that come from these spells give a 'percentage' of the damage inflicted on the victims.
In G'flott's case, the spell produces a noxious toxic gas cloud, which affects all creatures with nostrils. Its damage against trolls is quite reduced, though (similar, or even less, than Pragi's).
In the past, it was hardly ever used at all, as the component was a bit hard to come by in large enough quantities, and it was allegedly quite slow to cast. It has been tweaked of late, but I doubt it is still used much (sulphur-purchasing sites are still not as abundant as candle-buying places, and eyes are for free, of course...), even though I employ it out of curiosity and free mind space.

Where is it? Smells floating in the air in the form of evil cloud make it suitable for the Invoakatyons in thee Mysterie of Wynd grimoire, at Unseen University, which is were it lies.

What does it require? A block of sulphur, which is consumed.

What skills do I need? Evoking, Air, Dancing, Fire, Air (2)

Has it worked? A correct output should be something like this:

You prepare to cast G'flott's Olfactory Nightmare.
You carefully inspect the block of sulphur.
You take a deep breath.
You begin to tap the block with your fingetips, beating a complex tattoo as sulphur dust starts to swirl around you.
Your tapping becomes louder and faster and suddenly the cloud of sulphur ignites.
The cloud begins to move away from you.
The cloud rolls unstoppably across everything around you.
The cloud makes (see note).
The cloud dissipates.

Help Information:

G'flott's Olfactory Nightmare - bad smell.

G'flott's Olfactory Nightmare is a first order offensive spell that creates a cloud of noxious gas, covering everything nearby and harming living things with respiratory systems.

Notes: As has been stated (and in a similar manner as EHA), the damage caused is percentual to the victim's top amount of hit points. Some research had to be developed here, as the marginal use of the spell meant that an ordered list of the damage outputs was nowhere to be found. I am not absolutely sure about the order of the first two, so any information that would confirm/rebuke this table would be greatly appreciated:

The cloud makes the xxx gasp for air (0-15%)
The cloud makes the xxx cough (15-35%)
The cloud makes the xxx wheeze painfully (35-55%)
The cloud makes the xxx gag and look very ill (55-75%)
The cloud makes xxx choke horribly (75-90%)
The cloud asphyxiates xxx (+90%)