When business owners think about workplace health and safety, they tend to think about slips, trips, and falls. Ergonomic workstations. Fire exits. What they rarely consider — until it forces itself upon them — is the air their employees breathe, the surfaces their staff touch, and the invisible contamination that can turn a productive office into a liability. In 24 years of forensic contamination assessment, I have seen commercial properties generate some of the most complex and costly contamination disputes I have encountered. The stakes are different from residential — but often higher.

Types of Contamination in Commercial Properties

Commercial properties present a contamination profile quite distinct from residential settings. The building systems are more complex, the occupant density is higher, and the legal framework governing workplace safety creates obligations that do not exist in domestic environments.

Mould from HVAC Systems

The single most common contamination issue I encounter in commercial properties is mould growth within HVAC systems. A commercial heating, ventilation, and air conditioning system does more than regulate temperature — it circulates and recirculates air throughout the entire building. When mould colonises the cooling coils, drain pans, ductwork, or filters, the system becomes an active contamination distribution network, delivering spores to every space it serves.

The conditions inside commercial HVAC systems are ideal for mould growth: condensation forms on cooling coils, drain pans collect standing water, filters trap organic debris that serves as a nutrient source, and the dark, enclosed environment eliminates the UV light that naturally inhibits fungal growth outdoors. A single contaminated air handling unit can elevate indoor mould concentrations across an entire floor plate, affecting dozens or hundreds of workers simultaneously.

Species commonly identified in commercial HVAC systems include Aspergillus niger, Aspergillus fumigatus, Penicillium species, and Cladosporium. While these are common environmental fungi, sustained elevated exposure in an enclosed workplace — where workers spend 8 or more hours daily, five days per week — presents a fundamentally different risk profile from transient outdoor exposure.

Drug Residues in Warehouses and Industrial Properties

Warehouses and light industrial properties have become increasingly common locations for clandestine drug manufacturing. The appeal is obvious: large enclosed spaces, chemical storage capability, ventilation systems designed for industrial use, and — critically — less scrutiny than residential premises attract. When these properties are subsequently leased to legitimate businesses, the residual contamination from manufacturing activities can persist on surfaces, in ventilation systems, and in porous building materials for years.

I have assessed commercial properties where the new tenant’s staff reported persistent headaches, skin irritation, and respiratory symptoms within weeks of occupancy — symptoms that were ultimately traced to methamphetamine residues from previous manufacturing activities. The cost of remediation in a large warehouse can exceed $200,000, and the question of who bears that cost — outgoing tenant, landlord, or incoming tenant — invariably becomes a legal dispute.

Bacteria in Shared Facilities

Commercial buildings with shared amenities — bathrooms, kitchens, break rooms, and gymnasiums — present ongoing bacterial contamination risks. High-traffic facilities used by hundreds of occupants generate bacterial loads that routine cleaning may not adequately manage, particularly on porous surfaces such as grout, carpet, and upholstered furniture. In buildings with inadequate ventilation in wet areas, the combination of moisture and organic matter creates persistent bacterial reservoirs.

Office Fit-Out Contamination

New or recently renovated offices can harbour significant chemical contamination from building materials and furnishings. Volatile organic compounds (VOCs) — including formaldehyde, benzene, toluene, and xylene — off-gas from composite wood products, adhesives, paints, carpet backing, and office furniture. In a well-ventilated building, these compounds dissipate relatively quickly. In a sealed, mechanically ventilated commercial building — particularly one with recirculating air handling — they can accumulate to concentrations that produce occupant symptoms.

Formaldehyde is of particular concern. It is classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC) and is commonly found in medium-density fibreboard (MDF), particleboard, and plywood used in office cabinetry and workstations. The Australian standard for workplace formaldehyde exposure is 1 ppm (8-hour time-weighted average) under the Workplace Exposure Standards for Airborne Contaminants, but many occupants report symptoms at concentrations well below this threshold.

Work Health and Safety Obligations

The Work Health and Safety Act 2011 (and equivalent state legislation in non-harmonised jurisdictions) imposes clear obligations on persons conducting a business or undertaking (PCBUs) to manage health risks in the workplace. These obligations extend explicitly to environmental contamination.

Section 19 of the WHS Act requires a PCBU to ensure, so far as is reasonably practicable, the health and safety of workers while at work, and that the health and safety of other persons is not put at risk from work carried out. “Health” in this context is not limited to physical injury — it encompasses exposure to harmful substances, poor air quality, and environmental conditions that may cause illness.

For commercial properties, this means both the tenant operating a business and the landlord or building manager can be PCBUs with concurrent duties. A tenant who fails to investigate occupant health complaints is in breach of their duty, just as a landlord who fails to maintain the HVAC system or repair a leaking roof is in breach of theirs.

Under Section 84 of the Act, workers have the right to cease work if they have a reasonable concern that continuing to work would expose them to a serious risk to their health or safety. I have seen cases where entire floors of commercial buildings were vacated by workers exercising this right following mould discoveries — with significant business interruption consequences for the tenants.

Tenant vs Landlord Responsibilities

The allocation of responsibility for contamination in commercial leases is one of the most disputed areas of commercial property law, and the answer is never as simple as either party would like.

Landlords are generally responsible for the structural elements of the building: the roof, external walls, building envelope, base building HVAC systems, common area plumbing, and the overall condition of the premises at lease commencement. Pre-existing contamination — whether from previous tenants’ activities, building defects, or environmental conditions — typically falls within the landlord’s responsibility.

Tenants are generally responsible for maintaining the premises in a clean and safe condition during their tenancy, managing contamination arising from their own operations, and — depending on lease terms — maintaining tenant-installed fit-out and supplementary HVAC equipment.

The grey areas are extensive. A mould problem caused by a landlord’s failure to repair a roof leak, but exacerbated by the tenant’s failure to report the leak promptly, creates shared liability. HVAC contamination in a base building system maintained by the landlord but loaded beyond design capacity by the tenant’s occupancy density involves both parties. Drug contamination from a previous tenant that the landlord did not test for before re-leasing creates exposure for the landlord, but the incoming tenant’s failure to conduct pre-lease due diligence may limit their claim.

Testing During Lease Disputes

Contamination testing frequently becomes critical during commercial lease disputes, and the quality and independence of the assessment can determine the outcome. In my experience, the most common dispute scenarios involve:

• End-of-lease disputes — the landlord claims the tenant caused contamination during their occupancy; the tenant argues the contamination was pre-existing. Without baseline testing at lease commencement, these disputes are extremely difficult to resolve.
• Make-good disputes — the tenant’s make-good obligations may or may not extend to contamination remediation, depending on lease terms and the origin of the contamination.
• Rent abatement claims — tenants may seek rent reduction or abatement where contamination renders premises unsuitable for their intended use.
• Early termination — tenants may seek to terminate leases where contamination constitutes a breach of the landlord’s obligation to provide premises fit for purpose.

In all of these scenarios, the independence of the assessor is paramount. An assessment conducted by a company with remediation interests will face credibility challenges in any legal proceeding. At Test Australia, we maintain strict independence from remediation and cleaning companies — our only interest is in providing accurate, defensible results. This independence is not a marketing position; it is a fundamental requirement for assessment evidence to withstand scrutiny.

Pre-Purchase Commercial Due Diligence

Purchasing a commercial property without contamination assessment is, in my professional opinion, a significant risk that no competent advisor should allow a client to take. The cost of a comprehensive pre-purchase assessment is typically between $2,000 and $8,000 depending on property size and complexity — a trivial sum relative to the purchase price and the potential remediation costs.

Pre-purchase assessment for commercial properties should include:

• Historical use investigation — understanding what the property was previously used for, particularly any industrial, manufacturing, or storage activities
• Visual inspection — identifying visible contamination indicators including water damage, staining, mould growth, and evidence of chemical use
• HVAC inspection — internal examination of air handling units, ductwork, and cooling systems
• Air quality sampling — baseline indoor air quality assessment including mould spore counts and VOC screening
• Surface sampling — targeted sampling based on property history and visual indicators
• Moisture mapping — identifying current and historic moisture intrusion pathways

The results provide a clear picture of the property’s environmental condition at the time of purchase, informing both the purchase decision and any remediation costs that should be factored into the price negotiation.

HVAC Contamination Assessment

Given that commercial HVAC systems are the primary contamination vector in most office buildings, a dedicated discussion of HVAC assessment methodology is warranted.

A thorough HVAC contamination assessment includes inspection of air handling units (AHUs) — opening access panels to examine cooling coils, drain pans, supply and return plenums, and filter housings. Swab samples should be collected from cooling coil surfaces, drain pan surfaces, and internal ductwork walls. Air samples should be collected from both supply registers and return grilles to quantify what the system is delivering to occupied spaces versus what it is drawing back.

Moisture readings within the AHU and ductwork identify condensation and standing water conditions that support microbial growth. Filter condition assessment determines whether filters are adequately sized, correctly installed, and changed at appropriate intervals.

In my experience, the most overlooked component of commercial HVAC assessment is the drain pan. When condensate drain pans become blocked or develop biofilm, they create a permanent moisture reservoir within the air handling system. Every cubic metre of air passing over that reservoir picks up microbial contaminants and distributes them through the ductwork. A blocked drain pan can contaminate an entire building within days.

Business Interruption Considerations

For commercial property contamination, the direct cost of testing and remediation is often dwarfed by the indirect costs of business interruption. When a contamination finding requires remediation of occupied spaces, the business impact can include:

• Temporary relocation of staff — including the cost of alternative premises, IT infrastructure, and productivity losses during transition
• Loss of revenue during closure or reduced operations
• Client relationship damage from service disruption
• Staff health claims and workers’ compensation
• Reputational damage, particularly for client-facing businesses

Business interruption insurance may cover some of these costs, but coverage depends on the specific policy terms and whether contamination is a covered peril. Many standard business insurance policies exclude gradual contamination, covering only “sudden and accidental” events. Reviewing your policy with your broker before a contamination event occurs is vastly preferable to discovering exclusions after the fact.

The Cost-Benefit of Proactive Testing

The mathematics of proactive versus reactive contamination management in commercial properties is unambiguous. Annual HVAC inspection and air quality monitoring for a typical office building costs between $3,000 and $10,000 — depending on the number of air handling units and the floor area served. Against this, a single mould remediation event in a commercial building can cost $50,000 to $500,000, excluding business interruption. A lease dispute driven by contamination findings can generate legal fees exceeding the remediation cost itself.

Proactive testing also provides documentary evidence of ongoing environmental management — evidence that demonstrates compliance with WHS obligations, supports insurance claims when they arise, and protects against future liability. An employer who can demonstrate annual air quality monitoring and HVAC maintenance is in a fundamentally stronger legal position than one who cannot.

If you own, manage, or lease commercial property, I encourage you to contact us to discuss a testing and monitoring programme tailored to your property. The cost of knowing is always less than the cost of not knowing.