Measures for the employee against exposure to contaminated SF6 during maintenance work

Before you begin

• Ventilate the space before you enter.  If mechanical ventilation is available, switch it on. 
• Measure the SF6 concentration in the high voltage spaces (equal to or higher than 50kV) or if indicated on the work plan. Take the measurements low down at floor level. For low concentrations of SF6 ventilation is sufficient.
  • If you are in a space for a short time, for example to position the measuring apparatus, the concentration of clean SF6 may not be greater than 6000 mg/m3 (1000 ppm). 
  • If you are entering a space where it is possible that leaked SF6 may be present, the concentration may not be higher than 1200 mg/m3 (200 ppm).
  • If you will be remaining in a space longer and if you are carrying out work activities on SF6 equipment in the space, the concentration may not be higher than 60 mg/m3 (10 ppm).

During the work

• Do not smoke and do not use an open flame in a space with any SF6-installations or in open spaces which are connected with spaces where SF6-installations are present.
• Do not eat or drink in a space with any SF6-installations or in open spaces which are connected with spaces where SF6-installations are present.
• Evacuate SF6-gas as deeply as possible into pressure tanks and/or gas bottles.
• Rinse three times with air/nitrogen.
• Bring the compartment to atmospheric pressure.
• Wait at least one hour before opening compartments in which there may have been electric arcs and/or decomposition.  This is in order to allow any powder decomposition to settle. When powder decomposition has taken place (or this is suspected) you must wear the following personal protective equipment:
  • Disposable overall (class 5 or 6)
  • Rubber or neoprene gloves
  • Rubber or neoprene boots
  • Full face mask with B2 P3 filter (filter is a single use filter)
• Measure the SF6 concentration (lower than 60 mg/m3  = 10 ppm) on opening the installation.
• Continuously measure the oxygen level  in the installation as it is rinsed with nitrogen.  The oxygen level must be 20-21%.
• Remove loose dust with a vacuum cleaner with a high energy particulate air filter on the exhaust side. 
• Remove any dust which adheres with a non-fraying dry material
• After cleaning you can continue working in the compartment without the above personal protective equipment.

When the work is finished

• Clean the tools and personal protective equipment with a vacuum cleaner or with a non-fraying dry cloth or a 10% soda solution.
• Clean the vacuum cleaner compartment with a cloth drenched in 10% soda solution and place the filter and the vacuum cleaner dust bag in a 10% soda solution for 24 hours. 
• Dispose of the waste as hazardous waste.