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How often should your ducts be cleaned?HVAC system hygiene is an important part of the operation of any building and depending on the building use it can be absolutely critical. The awareness of indoor air quality (IAQ) is increasing every day. Regular visual inspections are the best way to realise when HVAC cleaning and decontamination should be conducted. Research concludes that new ducting should be cleaned before occupancy begins.
 ContaminationIt is not uncommon to find debri left over from construction with no explainable reason for their presence and no possibility of these items entering the ducting in the normal course of operation. Such items include old newspapers, HVAC drawings, hard hats, torches, tools, bird nests, lunch boxes, takeaway wrappers and an array of other items. Depending on usage and history of the building and the materials used to constuct it, HVAC systems may become contaminated with
hazardous materials. Leaking water pipes above ducting will eventually corode the ducting and allow water to enter the ducting. The presence of of high humidity or water damage in ductwork can lead to significant microbiological contamination. Biological contaminants, caused by the accumulation of dust and debri combined with appropriate moisture levels that are present in HVAC systems, that can be potentially distributed to occupied spaces include:
Musty odours from supply diffusers may indicate fungal growth within the HVAC system, but there could be other sources also. Visual Inspection ProgramACR 2002 Assessment, Cleaning & Restoration of HVAC systems, sets out a visual inspection program that should form part of all facilities Indoor Air Quality Management Plans and Procedures. The table below indicates HVAC cleanliness inspection schedules for different building use classifications.
Source: Scott Summerville, B Sc., MAIRAH, MIAQA - Indoor Air Quality Conference, August 2002. Kitchen exhaust ducts
Legal IssuesGeneralAustralian lawyers have predicted an increase in claims for "Sick Building Syndrome" and "Building Related Illnesses" as Australian building occupants become more likely to seek remedy to complaints in the courts.Their predictions for the increase are based on:
In broad terms we can divide the issues into two categories:
Building Owners and Occupiers - Duties of CareAt common law, occupiers of land and premises owe a duty of care to persons entering their premises and may be liable for illness (injury) suffered by them. This liability is governed by the general principles of negligence.To determine an occupier's liability all the relevant circumstances are considered; in particular:
There must be a reasonable foreseeability of a real risk of injury to the entrant or to the class of person of which the entrant is a member. A risk of injury which is unlikely may be foreseeable so long as the risk is not farfetched or fanciful. An occupier's obligation is measured by the standard of reasonable care. A building owner may be liable for injury suffered by entrants caused by faulty air conditioning where the building owner has been warned of the defect in the air conditioning by an expert. Similarly, if a manufacturer warns a building owner of a risk involved in the use of a faulty air conditioning unit and injury is suffered by people entering the building as a result of the defect, the manufacturer has fulfilled the common law duty of care it owes to the building owner. However, the building owner will be liable as an occupier for the injury suffered by the entrant. Australian standards, particularly AS 1668 Part 2 and AS/NZS 3666, are relevant to duty of care and it could be argued that the risks associated with the failure to meet these standards would probably be reasonably foreseeable. A defendant in an indoor air quality case whose building failed to comply with any relevant requirement of these standards would be hard-pressed to escape liability. Occupiers and owners each have responsibilities. Control is the primary factor in assessing liability. It is not necessary that a person should have the entire control over premises in order to be an occupier. Nor is it necessary to show exclusive occupation. It is sufficient if a person has some degree of control such as that given by a legal right to invite the Plaintiff to enter the premises. It is not necessary to be in actual physical possession of premises in order to be an occupier of them. In addition, there may be more than one occupier of the same premises. Two or more persons may be occupiers. Wherever there are two or more occupiers each is under a duty to use care towards persons coming onto the premises. This duty depends on the occupier's degree of control. Note that when a danger exists next to the area controlled by an occupier, it may owe a duty of care to persons injured by the danger whether or not it is in control or occupation of that area. When a Plaintiff has been forced to use adjacent land because of conditions on the occupier's land, liability is usually attributed to the first occupier, not to the occupier of the adjacent land. There are a number of legal defences to negligence, for example the voluntary assumption of risk. For a Defendant to have the benefit of the defence that the Plaintiff voluntarily assumed the risk of injury, the Defendant must prove on the balance of probabilities that the Plaintiff consented, expressly or impliedly, to the risk.Employers' Duties of CareProperty owners and managers also have obligations as employers. At common law, a worker injured in the course of employment could sue the employer in negligence. Common law negligence is established by proving the existence of a duty of care, the breach of that duty and a causal relationship between the breach of duty and the original injury complained of. At common law an employer owes a duty to take reasonable care for the health and safety of each of its employees.This duty requires that the employer provide:
The standard of care is reasonable care, and what is reasonable will depend upon:
It is important to stress that the duty is owed to each employee as an individual. If the risk is greater to one employee than to another - for example, because of an allergy or peculiar susceptibility - then the duty owed will be greater. Likewise, if the consequences of injury are greater. This duty cannot be passed to another by contract although, should an employer engage a contractor to maintain safe premises for the employer's employees, the employer may be able to recover from the contractor either in contract or in negligence in the event that the employer was found liable to an employee for failing to provide safe premises. Thus, it may be that the employer would be required to do all that is practicable to be satisfied that the HVAC system was safe and without risks to health. If the building owner refused to co-operate and there was evidence of a foreseeable risk that the building was contaminated, the employer may be required to remove its employees. This would be akin to shutting the factory should the risk warrant it. Duty of Care ConsequencesWhere a person sustains an injury caused by poor air quality due to a faulty HVAC system that person may have a claim against the building owner, employer tenant, manufacturer, and/or the designer or installer, of the system. Indeed all of these parties may be liable as follows:
Other Legal Issues Other legal issues include
Liabilities under these headings can be very strict. Once a causal connection is made between a plaintiff's illness and, for example, the air conditioning system serving a building then liability accrues regardless of the measures taken by the employer. A special case in point concerns passive smoking, i.e. inhalation of tobacco smoke by non-smokers. The Full Court of the Australian Federal Court found that there is considerable evidence of a connection between passive smoking and lung cancer, asthma and respiratory diseases. In the context of compensation available to employees for diseases attributable to or aggravated by their employment, the inhalation of cigarette smoke by non-smoking employees in the workplace has resulted in successful compensation claims for illness caused by passive smoking. Steps to Minimise Litigation RiskProtection from litigation is not just the realm of the building owner, occupier or the employer. In the event of a claim the plaintiff will often make a claim against multiple parties and in turn these parties will look to identify other defendants to whom they might, in turn, direct the liability. Apart from legal obligations and duties of care, relevant parties should exercise vigilance in additional areas including:
With reference to potential breaches of environmental statutes, corporate officers should take steps and develop a compliance system to enable them to demonstrate that they use "all due diligence" to prevent breaches of legislation. Such a compliance system must be supervised and reviewed to ensure its effective operation. In relation to risks, the best defence is to manage risks before claims are made. This involves an ongoing program of monitoring relevant environmental conditions in a workplace or building. The programs need to be well documented and any remedial action identified under the program should be addressed as failure to do so may provide incriminating evidence that proves no action was taken. Some programs adopted go further than ensuring environmental and OHS laws and standards are complied with and it is desirable that they do to minimise legal risks. In areas where scientific knowledge is evolving such as indoor air quality such a program should also monitor the state of the evolving knowledge and assess the implications of that knowledge. If scientific knowledge progresses in such a way as to indicate a particular risk in circumstances that are manageable, it will be wise to react to that knowledge. Any industry or commercial undertaking that does not take these steps will ultimately be more vulnerable to prosecution and civil liability. The Right To Healthy AirIn 2000, a WHO working group prepared nine statements on rights to healthy indoor air. These statements have been endorsed by other recognised bodies such as the International Society for Indoor Air Quality and Climate, have already entered the curricula of tertiary educational courses and have been used in lawsuits. The statements, without interpretation or comment, are:
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