Asbestos Licensing

Policy

Carbon monoxide (CO) poisoning within an asbestos enclosure (3/02)
James Skilling - Head of ALU

1 At the recent ALG meeting, it was agreed to produce a memo on this matter, in view of the potential serious repercussions resulting from the use of an LPG fuelled water heater in an asbestos enclosure. A similar memo was issued to ALPIs for information last month.

2 A situation arose resulting in three asbestos operatives having to be rescued from an asbestos enclosure after being overcome by carbon monoxide fumes. This is a further reminder to us all that other risks may be present in the work, besides the asbestos content of the insulation, coating etc.

Circumstances

3 The contract involved the removal of asbestos containing decorative coatings (DC) applied to concrete ceilings. A full enclosure with negative pressure units was set up. A cauldron of water was taken into the enclosure, the water to be heated by a propane burner. The cauldron was left to boil for about an hour or so to allow the steam to soften the DC. Three operatives then went into the enclosure to remove the DC using hand scrapers. The propane burner was still running.

4 After working for a while within this enclosure the operatives began to feel unwell and decided to get out. The first operative left the enclosure and decontaminated himself. After a few minutes he realised that his colleagues had not followed him out so he went back into the enclosure and found that they had both collapsed. The first operative exited the enclosure again, raised the alarm while in the air lock and collapsed himself. Construction personnel also working on the site rescued all three operatives who have since made a full recovery.

Surrounding events

5 HSE had visited the site during the setting up stage when it was established that 110 volt wallpaper stripping machines were to be used to help remove the DC. It appears that the licensed contractor then changed to the propane burner heated cauldron method after the enclosure had been completed. The method had been used successfully on a previous contract elsewhere so new equipment was purchased for this job.

6 It appears that during the work the enclosure ventilation may have been affected. A door in the building, between the air lock and the negative pressure unit, had been wedged open. This door may have closed, reducing the ventilation. In the confusion of the incident it is uncertain whether this door was open or closed.

Attendant risks

7 All heaters fuelled by natural gas or by LPG require an adequate supply of fresh air to ensure complete combustion and minimal formation of carbon monoxide. It is likely that the main factor in this incident would have been the carbon monoxide produced by the LPG burner, caused by incomplete combustion. The problems that have arisen with certain steam generating LPG fired wall paper strippers when used in confined spaces are directly mentioned in paragraph 24 of HSE Guidance Note EH43 entitled 'Carbon monoxide: health hazards and precautionary measures'. Any problem with inadequate ventilation would then only exacerbate the matter.

8 However, such a practice also produces other risks:

• steam displacing the oxygen;
  
• raised air temperature increasing heat stress problems;
  
• RPE pulling through very moist air may contribute to a poor face fit;
  
• fire risk from the naked flame burner with the plastic sheeting and other materials of construction.

9 Similar events may arise using portable generators again in areas with inadequate or restricted ventilation.

Preventive measures

10 Applying the requirements of COSHH, the exposure of persons to CO can be prevented by not using such equipment. Electrically heated stripping machines should be used instead (taking care with excessive water from the condensation). In circumstances where this LPG fuelled equipment has to be utilised, then a thorough risk assessment should be carried out, covering the matters mentioned in paragraphs 7 and 8 above as well as emergency arrangements.