Sterilisation Formulas

What is the Sterility Assurance Level (SAL) for sterilization processes?

Probability of not more than 1 viable microorganism in 1 million sterilized items'

What is the Inactivation Factor (IF), and how is it calculated?

Degree of reduction in viable population, calculated as IF = N₀/Nₜ (initial count/final count)'

What is the Decimal Reduction Time (D-value)?

Time to achieve a 90% kill of microorganisms at a specific temperature'

How can the D-value be calculated using the Inactivation Factor (IF)?

IF = 10^(t/D), where t is exposure time; e.g., IF = 10^6, t = 15 min, then D = 15/6 = 2.5 min'

What is the lethality (F₀) value, and what does the BP recommend?

Total thermal effect of sterilization; BP recommends F₀ ≥ 8 at 121°C'

How is the lethality (F₀) calculated?

F₀ = D × log(N₀/Nₜ), where D is the D-value and N₀/Nₜ is the reduction ratio'

What is the Z-value in sterilization?

Number of degrees (°C) to reduce the D-value by a factor of 10 (1 log unit)'

How is the Z-value calculated?

Z = (T₂ - T₁) / (log D₁ - log D₂), where T is temperature and D is the D-value'