Why doesn't incense set off my smoke detector?

Factual Questions
1

It seems like there’s quite a bit of smoke coming off the things, especially when I light more than one at once (which I often do).

When what seems like much less smoke wafts in from my barbeque on the patio, the detector goes off. But the incense never sets it off.

Is there something very different between the two types of smoke?

2

Maybe it has something to do with the type of smoke detector you have. I seem to recall that there are two types, and that one is better at picking up smaller smoke particles than the other.

Given incense’s tendency to hang around in the air a bit, I figure they’re pretty small smoke particles.