Today I'm going to talk about types of incense.
Now a diffuser doesn't hold incense exactly, but it does use a candle to make essential oils evaporate into the air and give off their lovely scent and beneficial chemicals. Unfortunately you need quite a bit for it to last a really long time. But a few drops should last about half an hour to an hour. In my opinion, a diffuser combines fire in the candle, water in the oil and air in it's dispersion. I have become quite attached to my diffuser over the past few weeks. One of my favorite oil combinations is two drops of lilac oil for every one of vanilla. I would say that the diffuser is a great substitution for normal incense for those who are sensitive to smoke. Just get the essential oils that collaborate with your magical work and put them in the basin. Then light the candle underneath and voila! You may want to test combinations first, to see if it smells good and isn't distracting or overpowering.
The next form of incense is one I think we're all familiar with. I know I used stick incense (or cone incense) before I even practiced witchcraft. Now, call me paranoid (I don't mind... It's kinda true) but I don't like the idea of not knowing exactly what is going into my spell work. There has to be some sort of binding agent in this incense, and I don't like not knowing what that is. So I use stick incense for spells only when I don't have the herbs to burn on charcoal (we'll get to that in a minute). But as always, use what works for you. Most stick incense doesn't sit right with me, so it would likely mess with my magic. Whereas for you it may work, so go with whatever feels right.
Loose herbal incense is what I understand to be the normal thing used by witches. You have an herbal mixture designed for your work, sometimes with oils mixed in, and you burn it on a charcoal block. You have to have sand underneath the block to absorb the heat. I do like using this method sometimes, but I think I may move away from it in favor of my diffuser. Cinnamon smells great on the charcoal block, but other herbal scents tend to get lost in the burning scent. I'll have to do a test to see which works best for me.