Carbon monoxide levels in air

Environmental indicators

Why we monitor carbon monoxide levels in air •
What's happening? •
Methods - how we monitor •
Results - data and trends •
More information

Why we monitor carbon monoxide levels in air

Carbon monoxide (CO) was measured in Hamilton on an annual basis over the period 1998 to 2005 and more recently over short 3-monthly periods in 2012, 2013 and 2014. Results show existing levels are either excellent or good, indicating that carbon monoxide is not of concern in Hamilton.

Carbon monoxide is an indicator of poor air quality. It’s associated with areas of high-density housing and busy roads. Waikato Regional Council continuously measures carbon monoxide levels in Hamilton.

Carbon monoxide is a poisonous gas that is colourless, odourless and tasteless. Waikato Regional Council monitors carbon monoxide to determine people’s exposure to it in areas where the air quality is suspected to be poor.

Carbon monoxide is poisonous because it attaches to our red blood cells better than oxygen - reducing the blood’s ability to carry oxygen around the body. Low exposure to carbon monoxide causes headaches, dizziness and nausea.

High exposure to carbon monoxide (for example, high concentrations present in enclosed areas) causes loss of consciousness and death.

Normally, when there is plenty of oxygen present, burning fuel will give off carbon dioxide (CO₂). The carbon (C) comes from the fuel and the oxygen (O₂) comes from the air. But, when there’s not enough oxygen present, only one oxygen molecule binds with a carbon – forming carbon monoxide (CO).

What's happening?

Most of the carbon monoxide in urban areas comes from motor vehicles and the burning of solid fuels, for example, burning wood and coal for domestic home heating and industry . Smaller amounts of CO are given off by gas burners and appliances.

The Waikato Regional Plan sets guideline concentrations for carbon monoxide at 30 mg/m³ for a one hour average and 10 mg/m³ for an eight hour average.

The National Environmental Standards for air quality include a standard for CO of 10 mg/m3 (eight hour average). This can be exceeded no more than once per year. We separate carbon monoxide levels into categories relative to the regional and national guideline.

The graphs show the percentage of air samples (eight-hour average) with carbon monoxide levels in the ‘excellent’, ‘good’ and 'acceptable' categories. No samples had carbon monoxide levels in the ‘alert’, or ‘action’ categories.

Methods - how we monitor

Monitoring sites for this specific indicator are marked in blue below:

(Map source: LAWA)
Carbon monoxide was monitored in Hamilton at Waikato Regional Council's Peachgrove Road monitoring site over the period 1998 to 2005. This is classified as a residential peak monitoring site in accordance with the Ministry for the Environment’s air quality monitoring site classifications.
Carbon monoxide has also been monitored in Hamilton at Waikato Regional Council’s Ohaupo Road monitoring site over the periods 1 October 2012 to 31 March 2013 and 6 March 2014 to 10 June 2014. This intersection was selected on the basis of it having been identified as a busy traffic site.
Carbon monoxide concentrations are measured continuously and are logged as 10 minute averages. Hourly and eight hour averages are derived from 10 minute data.
Carbon monoxide monitoring commenced at the Peachgrove Road site in November 1997 and finished in July 2005.
While data are collected continuously, several periods of missing data have occurred. The largest of these are:
- November 1 to December 22, 1998
- October 5 to November 17, 1999
- January 22 to February 13, 2001
- August 29 to September 16, 2002
- February 24 to March 19, 2003
- April 18 to May 18, 2003
- February 24 to March 18, 2004
- April 17 to May 17, 2004.
More recently, carbon monoxide has been monitored continuously at the Ohaupo Road monitoring site over the short survey periods 1 October 2012 to 31 March 2013 and 6 March 2014 to 10 June 2014.
Monitoring is carried out using an advanced pollution instrumentation (API) analyser. This is a continuous analyser that measures carbon monoxide concentrations using gas-phase infra-red absorption.
The more recent monitoring at the Ohaupo Rd site has been carried out using an Ecotech ML/EC 9830 CO analyser (gas phase infra-red absorption).

How this indicator is compiled

Monitoring results are reported in relation to the Waikato Regional Plan, using the Ministry for the Environment air quality indicator reporting framework outlined in the table below. This framework is used to report on air quality for a range of contaminants relative to their respective guidelines.

Table 1: Ministry for the Environment categories for air quality

Category	Value relative to guideline	Comment
Excellent	Less than 10% of the guideline	Of little concern
Good	Between 10% and 33% of the guideline	Peak measurements in this range are unlikely to affect air quality
Acceptable	Between 33% and 66% of the guideline	A broad category, where maximum values might be of concern in some sensitive locations but generally they are at a level which does not warrant dramatic action
Alert	Between 66% and 100% of the guideline	A warning level, which can lead to the guideline being exceeded if trends are not curbed
Action	More than 100% of the guideline	Exceeding the guideline is a cause for concern and warrants action if it occurs regularly

Tables 2 and 3 show the percentage of times carbon monoxide levels fell into each category and the maximum level for the year of monitoring.

Table 2: 1998-2014 one-hour carbon monoxide levels at Hamilton

Year	Categories					99.7 percentile (mg/m³)	Maximum value (mg/m³)	Number of times levels exceeded the proposed regional guideline
	Excellent	Good	Acceptable	Alert	Action
1998	98%	2%	0%	0%	0%	7	9	0
1999	99%	1%	0%	0%	0%	4	7	0
2000	100%	0%	0%	0%	0%	4	5	0
2001	98%	2%	0%	0%	0%	8	9	0
2002	99%	1%	0%	0%	0%	6	10	0
2003	99%	1%	0%	0%	0.0	6	7	0
2004	97%	3%	0%	0%	0%	7	9	0
2005	98%	2%	0%	0%	0%	4	6	0
2012	100%	0%	0%	0%	0%	1	1	0
2013	100%	0%	0%	0%	0%	1	1	0
2014	91%	9%	0%	0%	0%	3	5	0

Table 3: 1998-2014 8-hour carbon monoxide levels at Hamilton

Year	Categories					99.7 percentile (mg/m³)	Maximum value (mg/m³)	Number of times levels exceeded the proposed regional guideline
	Excellent	Good	Acceptable	Alert	Action
1998	84%	16%	1%	0%	0%	5	5	0
1999	92%	7%	0%	0%	0%	3	4	0
2000	97%	3%	0%	0%	0%	2	3	0
2001	86%	13%	2%	0%	0%	7	7	0
2002	88%	12%	0%	0%	0%	4	5	0
2003	93%	6%	1%	0%	0.0	5	5	0
2004	84%	14%	1%	0%	0%	6	7	0
2005	81%	18%	0%	0%	0%	3	4	0
2012	99%	0%	0%	0%	0%	1	1	0
2013	100%	0%	0%	0%	0%	1	1	0
2014	100%	0%	0%	0%	0%	2	3	0

National ambient air quality guidelines for carbon monoxide are:
- 30 mg/m³ – 1-hour average.
- 10 mg/m³ – 8-hour average.
National Environmental Standard for Air Quality for carbon monoxide is:
10mg/m³ - 8-hour average (1 allowable exceedance per year.)
Waikato Regional Council has carried out carbon monoxide monitoring in Hamilton only. Results from Hamilton suggest that carbon monoxide concentrations in other areas are unlikely to be of concern.
Waikato Regional Council, 1999: Environmental Monitoring Technical Manual. Waikato Regional Council, Hamilton. (unpublished).
Environment Waikato, 2003: Quality Assurance Procedures Manual for ambient air quality monitoring at Environment Waikato. Environment Waikato, Hamilton. (unpublished).

Results - data and trends

The data below was collected in 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2012, 2013 and 2014, and averaged 1 and 8 hourly.

Percentage of air samples with carbon monoxide levels in the excellent, good and acceptable categories

Graph showing % of air samples with carbon monoxide levels

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More information

This indicator will be updated in 2019.

Last updated June 2014