Don’t look now, but lurking around the average person’s abode are billions of bacteria, germs and allergens.

“People are exposed to millions of germs everyday, and these germs often live on surfaces around the home,” says Colleen Creighton, executive director of Alliance for Consumer Education, a nonprofit organization to promote responsible and beneficial use of products to ensure a safer, healthier and cleaner environment. “There is a growing body of evidence that some germs can survive on surfaces for as long as 72 hours, and that transmission from surfaces can contribute to infection.”

Most bacteria are harmless, but certain pathogenic bacteria, as well as viruses and allergens, are most unwelcome houseguests. Maintaining a home that minimizes the presence of bad microscopic critters depends on knowing where to direct your cleaning efforts to maximize your effectiveness.

The International Forum for Home Hygiene, based in Britain, specifies four types of sites and surfaces that pose the greatest risk for pathogen transmission.

1. Reservoirs: wet sites such as toilet bowls, drain traps and buckets.

2. Reservoir disseminators: dishcloths, wet cleaning utensils, sponges, showerheads, etc.

3. Hand contact surfaces: toilet handles and seats, basins and bath surfaces, cutting boards, kitchen work surfaces, kids toys, etc.

4. Other surfaces: all floors, beds and furniture.

Reservoir disseminators and hand contact surfaces pose a constant risk and require active vigilance. Cleaners, disinfectants and their close cousins, antimicrobial soaps, have been around for years and tackle those two highest risk areas, as well as the reservoirs themselves. But a growing list of household helpers is now helping homeowners eliminate the microscopic critters on other surfaces.

Halo Technologies Inc.’s Halo vacuum uses ultraviolet light to kill bugs that lurk in the carpet. Oreck Corp. builds key components of its Oreck XL Deluxe, Ultra and Titanium Series vacuums with an antimicrobial material, including the roller brush, handle and base plate. Cuprotex LLC manufactures pillowcases, sheets and mattress pads using a metal alloy-based technology that binds the natural antimicrobials copper, silver and zinc to fibers of cotton, polyester and bamboo (also a natural antimicrobial). American Textile Co.’s Allergy Relief bedding is made with a barrier fabric woven so tightly it prevents penetration from dust mites and their droppings. Oreck’s Oreck XL Professional Air Purifier captures and destroys airborne contaminants in a space of up to 600 square feet, while Lennox International Inc.’s air quality systems scrub the whole house of indoor air contaminants, preventing them from even settling on surfaces.

“There is no way that people can kill enough bacteria to eliminate them from our environment – they are just everywhere,” says Elizabeth Scott, biology professor and co-director of the Simmons Center for Hygiene and Health in Home and Community at Boston’s Simmons College. “But you might want to reduce the risk of a salmonella infection by hygienically cleaning the cutting board after preparing chicken, for example.”