Well I’ve only ever bought one, I think I bought it in a gas station actually so it was nothing fancy. It was a raspberry scented one and gave out an amazing smell for all of about five minutes; needless to say I wasn’t all that impressed. But to me they are basically a candle without the flame, which is a pretty genius idea especially for people with kids, or for clumsy folk or for people who’ve been known to go to bed whilst leaving candles burning…. (It happened only one time I swear!)
So how do they work? They’re quite a simple concept using evaporation. Porous reeds are placed into the bottle of fragrance, and then after a few hours the reeds will have become saturated with the concentrated scented oil. The natural air flow in your home or office spreads the scent throughout the room. The air will dry the reeds and so they’ll keep absorbing the fragrance. They basically work 24/7 and are quite inconspicuous.

I think they’re a great idea for the office. Obviously it might be a health and safety risk to have heaps of candles burning on your desk and not everyone likes air fresheners (I’ve yet to try one that doesn’t choke me or make me sneeze) so reed diffusers are perfect as they’re subtle but pleasant.
I know they’re not a new thing but I see a lot of brands only bringing them out now, I just hope they get them right.
I must invest in one, recommendations are welcome.