99.9% vs 99.99% - understanding what Log Kill means.

We've all come across a product that claims to kill 99.9% vs 99.99% of bacteria and thought to ourselves what is the real difference? Both sound highly effective, however there's a significant gap between the two. This is where Log Kill comes in to play.

What is Log Kill?

When disinfecting or sanitising a facility, the effectiveness of the product is measured by log reduction (often called log kill). Log reduction is based on the logarithmic scale, which tells us how much bacteria is reduced. Each log represents a 10-fold (90%) reduction in bacteria. For example:

So while the difference between 99.9% ands 99.99% may seem small on the label, in reality, it means 10 x fewer bacteria left behind!

Why does Log Kill matter?

Not every environment requires the same level of disinfection. Choosing the right product depends on where and what you are cleaning:

• Household cleaning - most retail sanitisers provide a 3 Log Kill (99.9%) which is usually sufficient for general household use where the risk of illness is relatively low

  
  

• High-risk areas (hospitals, food prep areas etc) - these environments require higher log kill disinfectants, often 4 Log (99.99%) or above to ensure harmful bacteria are effectively eliminated and hygiene standards are maintained.

Choosing the right cleaning product

Understanding log kill helps you choose the right disinfectant for the job. If a product with a much lower log kill is used in an environment that requires stronger protection, it may not eliminate enough bacteria. Instead of reducing risk, this can allow harmful bacteria to survive, spread, and potentially cause greater problems.

By selecting a disinfectant with the correct log kill level for the environment, you ensure effective protection, maintain compliance, and most importantly, keep people safe.

A difference of just 0.09% on the label can mean a tenfold difference in protection. Always check the log kill claims when choosing your cleaning and disinfecting products.

If you have a technical or product related question and would like some assistance, please reach out to us on technical.enquiries@cleenol.co.uk