The aim of this project is to increase awareness of the hazard of carbon monoxide, and increase the application of appropriate control measures. Carbon monoxide (CO) is believed to be by far the most common cause of poisoning both in industry and the home. The magnitude of the health hazard due to carbon monoxide, both fatal and non-fatal, is huge and poisonings are probably more prevalent than is
generally recognised.

The above paragraph is quoted from the ILO Encyclopaedia of Occupational Health & Safety and there is no reason to believe that workers in New Zealand are any less likely to be exposed to CO than workers in other countries.

The most serious accidents are where workers are exposed to high levels of CO (hundreds or even thousands of ppm), over a sufficient length of time, to cause obvious symptoms and acute illness requiring oxygen therapy, and urgent ambulance transport to hospital. 

Such incidents have occurred in recent years in fruit packing sheds or warehouses where fossil-fuelled forklifts have been operating. In one instance the forklift operator was found unconscious only minutes after speaking with their supervisor.

In another instance, two workers operated a petrol powered pump inside a water tank that they were cleaning. Both were admitted to hospital with CO poisoning, and required oxygen therapy for a number of hours.

In New Zealand, there are likely to be hundreds if not thousands of workers who are exposed daily to relatively lower levels of CO (measured in the tens of ppm). The workers themselves may be unaware that their low level ill effects (mild headache or nausea) are caused by CO. The difficulty with the hazard of CO exposure is that it is likely to be encountered in many workplace settings, since there are a variety of sources, across a variety of occupations.

Exposure to CO occurs in all of the traditional high hazard sectors that the Department of Labour works with, e.g. agriculture, construction, forestry and the extractive industries, as well as the general industrial and commercial sector.

The general industrial and commercial sector includes:

• Shipping and Ports: Operating forklifts in ship holds
• Food and Produce: Operating forklifts in chillers, freezers, sheds and warehouses associated with fruit, meat, seafood and vegetable storage and processing
• Motor vehicle repair: Running engines indoors
• Plant hire industry: Variety of fossil-fuelled plant hired out, for use in a place of work, remember section 18A.

Other Likely Settings:

• Aluminium and steel manufacture
• Coke and coal gas manufacture
• Confined spaces
• Diving (The compressed air used to fill cylinders or supply air directly, may be contaminated where the fresh air intake is too close to engine exhausts)
• Fire fighting
• Ovens and furnaces, foundries
• Parking buildings
• Transport (aviation, maritime, rail and road)

Workplace Exposure Standards

The current Workplace Exposure Standards (WES) were published by the Department of Labour in 2002. 

The Biological Exposure Index (BEI) for CO is 3.5 % as carboxyhaemoglobin (COHb).  If the COHb is maintained below 3.5 %, there should be no adverse effects upon a worker. Under most circumstances, this will be the case if the 8 hour average
exposure (TWA) does not exceed 25 ppm.  For protection against higher levels, for shorter periods, the sum of the exposures during the day at a particular level should not exceed the period indicated.

Concentration Exposure Period

• 200 ppm 15 minutes
• 100 ppm 30 minutes
• 50 ppm 60 minutes

The CO level should not exceed 400 ppm at any time during the day. The best measure of individual exposure to CO, is from analysis of a blood sample. However, this is an invasive procedure, and is usually only done as part of the diagnosis and treatment of CO poisoning.

---

Issued by the Department of Labour, New Zealand
http://www.osh.dol.govt.nz

No. 25 - January 2007