It's important that my seniors keep in mind that I have to follow important safety rules when using them- they fall into the same category as fireworks so I need to be sure to only use them in seasons when it is legal to use fireworks. In Phoenix, it is legal to set off novelty fireworks such as sparklers or smoke bombs in safe areas- like asphalt or concrete away from flammables. They can stain so keeping them away from garments or surfaces that are vulnerable (parking lots are perfect for smoke grenades) Regardless of the season or time of year I never use them in natural areas near grass, trees, etc- it's Arizona and basically almost always dry. I have used them on rocks if there is no brush, weeds, or sticks of any kind within a 100-foot radius. They are also expensive- they kind I use puts out a LOT of gorgeous amazing smoke and colour- but at $12 each for approximately 60-90 seconds we have to make every second of them count, and I only offer one per session if it is in an appropriate area.