Washing

The antimicrobial action of the laundering process results from a combination of mechanical, thermal, and chemical factors. Soaps and detergents function to suspend soils and exhibit some microbicidal properties. Hot water provides an effective means of destroying microorganisms at a temperature of at least 160°F (71°C) for a minimum of 25 minutes.

The use of chlorine bleach assures an extra margin of safety. A total available chlorine residual of 50 – 150 ppm is usually achieved during the bleach cycle. Chlorine bleach becomes activated at water temperatures of 135°F – 145°F (57.2°C – 62.7°C).

Chlorine bleach is an economical, broad-spectrum chemical germicide that enhances the effectiveness of the laundering process. Chlorine bleach is not, however, an appropriate laundry additive for all fabrics. Traditionally, bleach was not recommended for laundering flame-retardant fabrics, linens, and clothing because its use diminished the flame-retardant properties of the treated fabric. However, some modern-day flame retardant fabrics can now tolerate chlorine bleach. Flame-retardant fabrics, whether topically treated or inherently flame retardant, should be thoroughly rinsed during the rinse cycles, because detergent residues are capable of supporting combustion.

Although hot-water washing is an effective laundry disinfection method, the cost can be substantial. Several studies have demonstrated that lower water temperatures of 71°F – 77°F (22°C – 25°C) can reduce microbial contamination when the cycling of the washer, the wash detergent, and the amount of laundry additive are carefully monitored and controlled. Low-temperature laundry cycles rely heavily on the presence of chlorine- or oxygen-activated bleach to reduce the levels of microbial contamination.

When looking to disinfect laundry using bleach, follow these steps.

Use ¾ cup of bleach for a regular size load with an average soil level, and 1 ¼ cup for an extra-large or heavily soiled load. Using less than the recommended amount will not provide the correct amount of bleach active to disinfect the load.
Don’t overload the washer with too much laundry. Items need to circulate or tumble freely through the wash water for optimum cleaning.
Don’t overload the washer with items that have excess stain remnants still on the fabric. In that case it’s important to increase the amount of bleach to 1 ¼ cup.
Industrial/Commercial washing machines are usually automatically programmed according to recommended standards (temperature, chemicals dispense to specific loads, whites, colours etc.) Most Industrial/Commercial washing machines are maintained by a supplier the facility has a contract with.

Treatment with bleach alone reliably caused reductions of greater than 99.99%.