Should silent killer raise alarm?
Given that smoke detectors are mandatory for all new buildings, there is now a school of thought that carbon monoxide detectors, which are already available in all wholesalers, should also be a mandatory inclusion in new and existing homes. Adelle King reports.
Carbon monoxide (CO), produced from the partial oxidation of carbon-containing compounds, is often referred to as ‘the silent killer’ because it’s odourless, invisible and tasteless, and can cause significant health problems.
According to Energy Safe Victoria (ESV), in Australia there were 12 carbon monoxide poisoning fatalities resulting from gas appliances between 2006 and 2016.
These statistics have prompted calls for Australia to follow Canada’s lead and make carbon monoxide alarms mandatory in all new and existing premises.
Canadian province Ontario passed a law in 2014 requiring all homes that have at least one fuel burning appliance to have a carbon monoxide alarm installed after Toronto Public Health found carbon monoxide poisoning was the leading cause of accidental poisoning deaths in North America. The regulation is an update to Ontario’s fire code and is based on the recommendations of experts from fire services, rental housing industries and alarm makers.
Similar to smoke alarms, CO alarms monitor airborne concentration levels of carbon monoxide over time and sound an alarm when harmful levels are present. They sense high concentrations over a short period of time, as well as low concentrations over a long period of time.
There are three different types of sensors in these alarms, electrochemical sensors, biomimetic sensors and metal oxide semiconductors.
The most common CO alarms available on the market are electrochemical sensor alarms, which have electrodes immersed in a chemical solution. These electrodes can sense changes in electrical currents when they come into contact with carbon monoxide, which sets off an alarm. Biomimetic sensors feature a gel that changes colour when it absorbs CO, triggering the alarm, while metal oxide semiconductor alarms have a silica chip circuitry that detects CO and lowers the electrical resistant to trigger the alarm.
There is some controversy surrounding carbon monoxide alarms in Australia, with suggestions their performance can be affected by a range of factors and that they give consumers a false sense of security. However, advocates, such as the Chase and Tyler Foundation, argue that like smoke alarms, CO alarms do not stop CO from being produced but give occupants of a room warning if it’s present and are therefore the best way to prevent CO poisoning.
Honeywell Security and Fire, a supplier of CO alarms, says that although the public is largely aware of the dangers of CO poisoning and the incidence of deaths in Australia caused by CO poisoning is relatively low, there are still a number of incidents that have been caused by the actions of occupants rather than failure of equipment.
“The public seems to be unaware of how easily CO can be produced in the home and the specific threat it presents. There are still incidents of people relying on heating appliances using charcoal briquettes in a fully sealed bedroom, resulting in the production of a dangerous level of CO within the room. Therefore, CO detection should be mandatory in all premises which provide sleeping facilities,” says Honeywell Security and Fire industry affairs leader Keith Shinn.
In 2011 a private members bill was introduced by the then MP for Murray, Sharman Stone, requiring all residential properties with gas appliances to be fitted with carbon monoxide alarms. It had bipartisan support, which resulted in a Regulatory Impact Statement (RIS) published for the Department of Resources, Energy and Tourism to explore the costs and benefits associated with different regulatory approaches to address the risk of CO poisoning from gas appliances.
The RIS found that although the mandatory installation of CO alarms in all residential properties will lead to an 11.3% reduction in risk from CO poisoning, it was the poorest performing option in terms of net performance value and would cost the community more than $2.3bn in present value terms.
ESV says there are also concerns about the effectiveness of CO alarms, which should be considered as part of a solution rather than a silver bullet.
“The effectiveness of a CO alarm is highly dependent on its location relative to the offending appliance and pathway taken by the CO as it spills from the appliance. These alarms are also prone to nuisance tripping if installed next to gas cooking appliances, which are permitted to emit CO in accordance with strict emissions criteria that they must conform to,” says Energy Safe Victoria manager of type A gas appliance and component safety Enzo Alfonsetti.
However, Keith says the electrochemical cell technology that is most commonly used in CO alarms is extremely reliable and well developed.
“There is very little problem with regard to the false activation of CO alarms. The units are very reliable and are generally only activated by the presence of CO in the atmosphere. The fact that CO alarms have a cumulative operation means that they will not normally react to short spikes in the level of CO in the atmosphere in contrast with smoke alarms that are notorious for responses to conditions which simulate the presence of smoke,” says Keith.
The RIS also expressed concerns that, unlike smoke alarms, there are no Australian manufacturing or installation standards that ensure the reliability of CO alarms, and as a result their quality ranges considerably.
“The electrochemical cell in CO alarms depletes over time regardless of whether the alarm is exposed to CO or not. Some alarms do not indicate when the electrochemical cell is no longer operating and some alarms do not include a use-by date,” says Enzo.
According to Standards Australia, the CO alarms entering Australia generally conform to either US Standard UL2034 Single and Multiple Station Carbon Monoxide Alarms or British Standard EN50291-1 Electrical apparatus for the detection of carbon monoxide in domestic premises. Test methods and performance requirements.
A Standards Australia spokesperson said that since Australian homes do not have the centralised furnace systems and household draft seals with double glazing that are found in the US and Europe, it is difficult to achieve high concentrations of CO. This has meant demand for CO alarms hasn’t been high and there has been little need for a standard.
Keith says this could change though, as the introduction of energy efficiency requirements in Australian building codes has seen an increase in well-sealed buildings designed to achieve a higher energy rating, which could increase the risk of CO poisoning in the future.
Despite this, the RIS found that in an Australian context public awareness and safety campaigns would achieve the best cost/benefit ratio to reduce the risk of CO poisoning from domestic gas appliances.
ESV already runs a number of safety campaigns, including the ‘Cold Feet’ campaign highlighting the need for all types of gas heaters, including wall units, central heating units, space heaters and gas log fires, to be serviced every two years by a licensed gasfitter.
Electricians and electrical contractors play a vital role in the success of these campaigns by ensuring consumers understand the risks of CO poisoning and are aware of the need for regular maintenance of gas appliances by a licensed gasfitter.
“It is not expected that electricians know whether a gas heater or indoor water heater is open-flued or room-sealed but it is important they advise any customer with a gas heater or indoor water heater in their home that they should have it checked for correct operation by a qualified gasfitter following the installation of a kitchen range-hood or exhaust fan,” says Enzo.