It does not smell like flowers, it smells like a very bad wet fart. If it is in the air below 10 ppm, you will be able to smell it for a minute or so, longer for some folks. At higher concentrations, the H2S will kill your sense of smell, then you know you are in trouble. If you can't smell it, remove yourself from the situation because once your sense of smell disappears, you will have no idea what concentration of H2S you are dealing with. Here is some cut-and-paste information regarding H2S:

0.00047 ppm or 0.47 ppb is the odor threshold, the point at which 50% of a human panel can detect the presence of the compound.[16]
0.0047 ppm is the recognition threshold, the concentration at which 50% of humans can detect the characteristic odor of hydrogen sulfide,[16] normally described as resembling "a rotten egg".
OSHA has established a permissible exposure limit (PEL) (8 hour time-weighted average (TWA)) of 10 ppm.[17]
10–20 ppm is the borderline concentration for eye irritation.
20 ppm is the acceptable ceiling concentration established by OSHA.[17]
50 ppm is the acceptable maximum peak above the ceiling concentration for an 8 hour shift, with a maximum duration of 10 minutes.[17]
50–100 ppm leads to eye damage.
At 100–150 ppm the olfactory nerve is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger.[18][19]
320–530 ppm leads to pulmonary edema with the possibility of death.
530–1000 ppm causes strong stimulation of the central nervous system and rapid breathing, leading to loss of breathing.
800 ppm is the lethal concentration for 50% of humans for 5 minutes exposure (LC50).
Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath.

Finally, it is easy to confuse the odor from natural gas from your home gas line and any other source of processed natural gas with that of H2S. The gas companies add an odorant to the natural gas to make it smell bad because untreated natural gas has no innate odor that is easily detectable by the human nose, that sensory input device which is so easily affected by the environment, rendering it untrustworthy. Butanethiol, which smells like “skunk” and tetrahydrothiophene, which smells like rotten eggs, are the most frequently used as natural gas odorants. Their stink can easily be confused with the smell of H2S. A really good indication that you are dealing with H2S vs natural gas odors is to look around you. If there is a chemical plant, refinery, large oil or chemical storage tanks nearby, or a shallow pond full of rotting organic material, a swamp, muskeg, or other such standing water in a natural setting, odds are you are dealing with H2S. Around stagnating water, H2S levels are bound to be low due to mixing with air. Around a man-made structure, they will probably be higher since man has a tendancy to store stuff with large amount if dissolved H2S in it.

Robert N Pruden