Practical Guide: 1.2.2 Nassenheider Evaporator

The Nassenheider evaporator is an approved system for the controlled application of formic acid in varroa control. Correct handling as well as consideration of temperature, dosage, and safety measures are essential for the efficacy and tolerability of the treatment. The following information is based on the official Practical Guide 1.2.2 of the Swiss Bee Health Service.

Official Practical Guide – Summary

Practical Guide: 1.2.2 Nassenheider Evaporator

• Definition: The Nassenheider evaporator is an evaporation system for the release of formic acid in honey bee colonies over a defined period.
• Objective: Reduction of varroa infestation through uniform evaporation of formic acid.
• Prerequisites:
  • Use of the formic acid concentration specified in the practical guide.
  • Compliance with the recommended temperature ranges.
  • Application only after completion of the honey harvest.
• Important points for application:
  • Prepare and position the evaporator according to the instructions.
  • Leave the entrance open.
  • Monitor the evaporation rate and adjust if necessary.
• Safety:
  • Formic acid is corrosive and requires appropriate protective equipment.

► PDF of the official practical guide (DE)

► Official overview of practical guides (bienen.ch)
Note: Section Varroa control → 1.2.2 “Nassenheider Evaporator”.

Summary based on Practical Guide 1.2.2. Last review: 01/2026.

Learn more:

• Practical Guide 1.1 : Varroa Concept
• Practical Guide : 1.3.1 Treatment by spraying
• Practical Guide : 1.3.3 Oxalic acid sublimation
• Practical Guide : 1.6.4 Total brood removal
• Practical Guide : 1.5.1 Measurement of natural mite fall