Types of Ice Melt

Sodium Chloride

• Rock salt is the classic ice melt. You can spread its large crystals by hand or with a garden spreader. Rock salt manufacturer Morton rates its rock salt as effective to 5 degrees Fahrenheit. Salt can be irritating to pets' feet, though, and if it accumulates across a hard winter, it may kill grass and flowers along walks and driveways. Rock-salt crystals can also hitch a ride into your house on your shoes and damage inside surfaces.

Calcium Chloride

• Calcium chloride's tiny white pellets have become familiar on the sidewalks of most areas prone to snow. You can spread them more easily than rock salt, shaking them from a plastic jug, for example. They continue to melt at much lower temperatures than rock salt. Morton, for example, rates its straight calcium chloride as effective to -25 F. Some ice-melt brands promote "exothermic" properties. This simply means that the chemical produces heat when it reacts with water to form the brine. Calcium chloride is too expensive for use over large areas, such as roadways and parking lots, but it is sometimes offered in blends with salt. Like rock salt, calcium chloride can irritate pets and damage gardens and interiors.

Chlorides Plus

• Chlorides do such a good job of melting ice that some manufacturers have tried adding to them to compensate for their negative side effects. Morton, for instance, adds fertilizer ingredients to compensate for chloride damage to plants and a proprietary additive that it claims forms a protective gel on concrete. Revere Products offers a calcium-sodium blend (90 to 97 percent by weight) with "mineral supplements used in most farm animal feedstock" as more paw-friendly. The mineral supplements, however, are other chlorides, of potassium and strontium.

Chloride-Free

• Chloride salts can irritate animals' paws, prompting them to lick and then causing them to vomit from swallowing too much salt. Morton's pet-friendly ice melt uses urea. According to MegaGro, the manufacturer of the chloride-free product IceClear, urea can be ecologically damaging if it runs off into streams and ponds. Its chloride-free protect is a liquid containing potassium acetate. The company claims that the product is manufactured from organic materials and effective to -76 F.