Your icons could be a bit more clear. A bell could mean an alarm, or a reminder, or something other than noise. Same with lighting (does the sun mean source of natural sunlight, or just fully illuminated?). The poo could mean there's deep shit here. Etc. With icons, it helps to make them nearly immune to being misconstrued.
I suggest light bulbs for light (black for darkness, lit for light), a speaker for sound (like the Windows tray icon), a nose and stink lines for smell (the poo isn't a bad idea though!), crossed swords for a hostile encounter (a shield could mean safe or defensive or something other than encounter) while a speech bubble denotes a non-hostile encounter, etc.
You're using your icons to cover too broad a spectrum - their intent should probably not be to communicate the information about how much light there is or if smells are good or bad, but rather their role is to be like "Yo DM! Something smelly here, better pre-read this area!". Catching scanning eyes and focusing them on the further information. The DM is going to be expanding on the room description when he describes it to the players, so it serves no real purpose to have icons explain stuff to the DM since he needs to read the full room text anyway.
FYI as a practice, I've taken to including icons on the map rather than in the key - it helps to know which rooms are illuminated or have a monster or something in them when looking at the map because it helps with the ever popular "I listen at the door" action or in describing light coming from the next room. One of great importance is an icon to denote an immediate hazard in a room (like something the DM needs to inform the players ASAP because danger, like no air or unbearable heat or something) - I personally use an exclamation mark.