Powdered High Strength Calcium Hypochlorite (Ca(ClO)₂) is essential for a medic to keep in the team house or aid station in an austere environment. It can easily be bought, transported and reconstituted for many purposes…
Autoclaving instruments with high pressure steam is the industry standard for sterilization. This is why the SF Medical TACSET includes the infamous portable pressure sterilizer more commonly known to the rest of the team as the lobster pot. If you find yourself in a situation without the lobster pot there are some other techniques for high level disinfection which will get your surgical instruments cleaner than just wiping them on your pants. These techniques include using dry heat, boiling, microwave, UV exposure and chemical dips.
To use Calcium Hypochlorite for “sterilization” of surgical instruments be sure to grossly decontaminate with a wire or stiff bristle brush first. Then mix 75g of 70% strength Ca(ClO)₂ into a liter bottle to make a household 5.25% strength bleach solution. Contact time is 5-10mins. Once you have scrubbed in and made yourself as sterile as possible, remove the instruments drom the bleach bath and irrigate with sterile irrigation fluid before use. This solution contains approx 52,500ppm Hypochlorite.
One of the weaker solutions described below can also be used as long as contact time is increased. Soaking any longer than recommended will damage the instruments as it is a powerful oxidizer. Do not store in a metal container or in a container with a metal cap.
5 drops of this 5.25% solution can be used to purify a liter of suspect water in order to remove bacteria and viruses to make safe for drinking. This will not kill Giardia or Cryptosporidium cysts. Those must be filtered or purified in another manner. This also will not remove other pollutants such as chemicals or heavy metals.
To make a strong disinfecting solution for surfaces exposed to bodily fluids such as patient litters and other non-sterile equipment, mix 100mLs of the 5.25% solution with 900mL of clean water. This will make a 5250ppm or 0.525% solution. Another way to get this strength is to use 7g of the concentrated powder in a liter of water.
The JTS CPG on Invasive Fungal Infections recommends a 1/20th strength (Full strength is traditionally a .5%) solution of 0.025% Dakins solution that is used directly on wounds to kill pathogens. This has been especially usefully when contaminated dirt and soil is blasted into a wound inoculating it with invasive fungal species such as Aspergillis.
Irrigation with Dakins solution should only be done temporarily. If left on for 4-7 days straight while waiting for delayed primary closure we have seen muscle tissue become indurated and hard after marinating for these longer periods of time without serial washout and debridement. To make 0.025% Dakins solution mix 5mL of the household 5.25% in a liter bottle with a teaspoon of baking soda.
In order to test any of these concentrations, test strips can be purchased in bulk for different levels of chlorine.
Be sure to clearly label each bottle with the strength and date made. They should last more than a few months at the lower concentrations but are easy enough to make a new batch when needed.
When calculating remember that 1mg/liter is equivalent to 1ppm and that the amount of active ingredient varies and should be read from the bottle. Most commonly high test calcium Hypochlorite is found with 70% available chlorine.
Make Household 5.25% Bleach:5.25%=.0525
75g × 70%=52.5g Ca(ClO)₂ in 1L H₂O
Available chlorine in 1L=52,500ppm
0.025% Dakins Solution:
5mL of 5.25%=52,500ppm
5mL of 5.25%+995mL H₂O=0.02625%
JSOM Article: Field Sterilization in the Austere and Operational Environment A Literature Review of Recommendations
Will JS, Alderman SM, Sawyer RC. 16(2). 36 – 43. (Journal Article)
US Army Public Health Center: Using and Preparing High Strength Chlorine
Joint Trauma System Clinical Practice Guideline on Invasive Fungal Infections:
Prolonged Field Care and Joint Trauma System Clinical Practice Guideline on Acute Wound Management:
US CDC: Disinfection with Chlorine:
Ohio State University Medical Center PDF -How to Make Dakins Solution accessed from:
Washington State Department of Health Water Purification:
Calcium Hypochlorite Solution Calculator:
CDC Pool Disinfection and Testing: