Technically they are different products for very different purposes. In many cases, though, the chemical contents are very similar or even identical. In those cases, the valve controls whether you spray vapor (duster) or liquid (freeze spray). Although you can turn over the can to spray liquid, in the case of duster, and vapor in the case of freeze spray, you are taking a risk going outside the intended function of the product. For example, if using an HFC-152a based duster, we do not recommend using as a freezer because of its flammable properties.