Part 3: Asbestos removal in practice – negative pressure, air exchange and post-ventilation that make a difference

It is easy to focus on the demolition itself when talking about asbestos. But in practice, safety is often determined by what is happening around it:

• air flow
• negative pressure
• cleaning
• post-ventilation
• control and follow-up
• When those pieces work, the risk of spread is dramatically reduced.

Negative pressure in the decontamination zone – a basic requirement for indoor work

The Swedish Work Environment Authority (Arbetsmiljöverket) states that the decontamination zone during indoor decontamination work should be under negative pressure.

The aim is for the clean air to move into the zone – not for asbestos fibers to be forced out into the building.

Air exchange: At least 10 times per hour

The Swedish Work Environment Authority also raises a clear guideline:

• The air in the decontamination zone should be exchanged at least 10 times per hour.

They also describe examples of volume flow and that in larger spaces, several air purifiers may be needed to achieve good exchange.

Checking negative pressure – important to be able to follow up

The negative pressure needs to be able to be checked. The Swedish Work Environment Authority states that it is best to do this with a pressure drop meter, but that in smaller spaces it may be acceptable to check that the plastic is bulging inwards.

Post-work: Vacuuming, wet-wiping and post-ventilating

After the demolition work is complete, it is not “finished” immediately. The Swedish Work Environment Authority describes that you should:

• vacuuming and wet-wiping all surfaces
• post-ventilating the area
• and that it is advisable to leave an air purifier with a HEPA 13 filter and purify the air for another 4–12 hours before demolishing the airlock and plastic sheeting

This is due, among other things, to the fact that fine asbestos fibers can remain suspended longer and follow air currents.

Summary: Safe asbestos handling requires control in several stages

Asbestos is a risk that requires more than “the right protection” – it requires the right method, the right routines and the right technical measures.

A safe work process is based on:

• training and permits
• clear instructions
• containment and airlock
• negative pressure + air exchange
• cleaning + post-ventilation
• documented follow-up

Contact us if you want a solution you can trust – with the right equipment and smart control in your everyday work.

FAQ

How many air changes are needed for asbestos work?
The Swedish Work Environment Authority states that the air should be changed at least 10 times per hour in the decontamination zone.

What should you do after demolition is complete?
The Swedish Work Environment Authority describes that you should vacuum and wet-dry surfaces and ventilate before demolishing the enclosure and airlock.

How long should you ventilate?
They state that it is often appropriate to let fan units with HEPA 13 filters purify the air for 4–12 hours, but the time needs to be adjusted according to space, volume flow and air mixing.