Drug and Alcohol Testing in Australian Construction Under the WHS Framework

Drug and alcohol testing programs on Australian construction sites frequently cover only the directly employed workforce. That approach leaves a significant compliance gap because the obligations that principal contractors carry under the Model WHS Act extend well beyond their own employees to every worker on their site, regardless of who engaged them.

Sections 19 and 20 of the Model WHS Act establish the legal basis for this. Section 19 sets the primary duty of care: a person conducting a business or undertaking (PCBU) must protect the health and safety of workers and others at the workplace, so far as is reasonably practicable. Section 20 applies that duty specifically to anyone who manages or controls a workplace. A principal contractor who controls a construction site holds both obligations simultaneously and neither is limited to the workers on the direct payroll.

Four areas of compliance sit at the centre of this obligation: the shared duty framework and what it requires of principal contractors, the upstream duty concept and how it applies to subcontractor and labour hire arrangements, what a defensible pre-access testing protocol must include, and the specific impairment obligations that apply to high-risk construction work.

Principal Contractors Hold Site-Wide Duty Obligations, Not Just Obligations to Direct Employees

A principal contractor is required for every construction project valued at $250,000 or more, and carries obligations that go beyond those of an ordinary PCBU operating on a shared site. Under the Model WHS Regulations, a principal contractor must prepare a written WHS management plan before work commences, take all reasonable steps to obtain Safe Work Method Statements (SWMS) for all high-risk construction work, and manage risk across the site in a way that accounts for the full range of workers and work activities.

Three sections of the Model WHS Act define how duty obligations are structured across a multi-contractor construction site:

Section 16 establishes that where more than one person holds the same duty, each must discharge it to the extent of their capacity to influence and control the relevant matter. Duties cannot be transferred to another party, including a subcontractor, through a contract. A principal contractor that requires all subcontractors to maintain their own drug and alcohol policies has not discharged its own obligation. Both duty holders remain independently responsible.

Section 19 requires every PCBU to protect workers and others at the workplace so far as is reasonably practicable. In construction, "others" includes the workers of every subcontractor and labour hire firm on site, delivery personnel, inspectors and any other person whose presence on the site is connected with the work.

Section 20 applies to any person who manages or controls a workplace. A principal contractor that controls site access, sets induction requirements, coordinates SWMS compliance and directs the overall sequencing of work is exercising exactly the kind of management and control that creates a duty to the people at that workplace.

Applied to drug and alcohol testing, this framework produces a clear position: a principal contractor with genuine management and control of a construction site holds a duty to manage impairment risk for the full site population. A subcontractor's standalone drug and alcohol policy, which the principal contractor neither audits nor enforces, does not satisfy that obligation.

The following table sets out the legislative basis across harmonised jurisdictions. Victorian construction employers should note the divergence and seek jurisdiction-specific legal advice before applying this article's analysis to their operations.

Upstream Duties Place Drug and Alcohol Risk Management Squarely on the Principal Contractor

Upstream duties refer to the obligations a PCBU holds toward workers it causes to be engaged on a site, even where no direct employment relationship exists. Under Safe Work Australia's guidance on WHS duties in a contractual chain, a principal contractor that engages a subcontractor causes the subcontractor's workers to be engaged at the workplace. Those workers are, in the terms of the Act, workers of the principal contractor for the purposes of section 19. The principal contractor owes them a duty of care proportional to its capacity to influence and control their work environment.

On a construction site where the principal contractor manages the induction process, controls site access, sets the site rules, coordinates SWMS activity and has the authority to direct or remove workers, that capacity is substantial. The practical implications for drug and alcohol compliance are significant:

1. The principal contractor cannot rely on a subcontractor's drug and alcohol policy as its own compliance measure and it must have an independent policy that covers all workers accessing the site, regardless of who employs them
2. Subcontractor agreements should specify drug and alcohol testing requirements as a condition of site access, but those clauses do not transfer the principal contractor's duty to the subcontractor; they establish a contractual expectation alongside, not instead of, the regulatory obligation
3. The principal contractor must have the capability to test, record and act on results across the full site workforce, not only its direct employees
4. Labour hire arrangements add a further layer: the labour hire agency holds its own duty as a PCBU toward the placed worker, but the principal contractor as the controlling workplace party holds concurrent obligations toward that same worker

The last point matters practically. A labour hire worker who arrives on site having tested positive at another location, or who has not been tested at all, presents a risk that neither the subcontractor agreement nor the labour hire contract addresses in real time. The principal contractor is the party with the authority to act at the point of access — and therefore the party with the responsibility to have a system in place that does so.

Audit-ready result management across a full contractor workforce is what makes this obligation operationally manageable, particularly on large commercial sites where dozens of subcontractors may be active simultaneously.

A Pre-Access Testing Protocol Needs to Cover the Full Site Workforce, Not Just Direct Employees

A defensible pre-access drug and alcohol testing protocol for a construction site is not merely a drug and alcohol policy, it’s the operational component of that policy. The policy sets the framework; the protocol specifies who is tested, when, by what method and what happens when a result is returned. Both documents need to be in place and aligned before the first worker sets foot on site.

Oral fluid (saliva) testing conducted under AS/NZS 4760:2019 is the appropriate method for pre-access and reasonable-suspicion testing in construction environments. The detection window for oral fluid testing reflects recent use (typically within the past 24 to 48 hours) which makes it directly relevant to a worker's fitness for duty at the time of testing. Urine testing under AS/NZS 4308:2008 remains appropriate for return-to-work monitoring and rehabilitation oversight, where a longer detection window supports ongoing accountability. Breath alcohol testing must be conducted using devices compliant with AS 3547:2019. Saliva drug test kits calibrated to AS/NZS 4760:2019 and designed for field conditions such as the DrugSense DSO8 Plus V3 and DrugSense OraScan Saliva Drug Test Cassette V5, support the chain-of-custody requirements that make results defensible in a WHS investigation or Fair Work proceeding.

A pre-access protocol that covers the full site workforce must address the following elements:

• Scope: All workers accessing the site: direct employees, subcontractor workers, employees of subcontractors, labour hire workers, owner-operators and any other person performing a work function on site
• Testing triggers: Pre-access before first site entry, random testing on an ongoing basis, post-incident testing following any notifiable or potentially notifiable event, and reasonable-suspicion testing where a supervisor or manager observes signs of impairment
• Testing method: Oral fluid testing under AS/NZS 4760:2019 for pre-access and reasonable-suspicion testing; breath alcohol testing using AS 3547:2019-compliant devices for all alcohol screening
• Positive result procedure: A documented response process specifying immediate work restriction, notification, support pathway referral and, where applicable, confirmation testing
• Record-keeping: All test results, chain-of-custody documentation and follow-up actions must be captured in a format that supports audit and, if required, legal proceedings; paper-based systems on multi-contractor sites create gaps that become visible under investigation
• Consistency: The protocol must apply equally across all worker types — applying testing requirements to subcontractor workers but not direct employees, or vice versa, creates both a fairness problem and a legal exposure

Drug and alcohol management sits within the WHS management plan, not alongside it as an optional annex. Principal contractors who treat the testing protocol as a standalone document risk creating an internal inconsistency between their documented site safety framework and their actual operating practice.

Workers Performing High-Risk Construction Work Face Greater Impairment Consequences and So Do the Contractors Who Direct Them

High-risk construction work (HRCW) is defined under section 291 of the Model WHS Regulations and encompasses approximately 18 categories of construction activity that carry a serious risk of fatal or serious injury. Impairment materially increases that risk in each of them. The categories most directly relevant to drug and alcohol testing obligations include:

The regulatory requirement for HRCW is the SWMS. A PCBU carrying out high-risk construction work must prepare a SWMS before that work commences and provide a copy to the principal contractor. The principal contractor must take all reasonable steps to obtain those statements and take all reasonable steps to have work carried out in accordance with them. Receiving a SWMS is a necessary step. A SWMS filed in the site office does not demonstrate that the workers performing the work were fit for duty at the time it was carried out. The principal contractor remains responsible for the conditions under which HRCW is conducted on its site.

Separate from HRCW, certain construction roles require a high-risk work licence (HRWL) under Schedule 3 of the Model WHS Regulations. Crane operators, riggers, scaffolders, doggers, forklift operators and others performing HRWL-class work must hold a valid licence to do so. Impairment in an HRWL holder creates a compound risk: the physical danger of impaired operation and the potential that their conduct is inconsistent with the conditions under which the licence was granted. Principal contractors should verify HRWL currency and fitness for work as integrated components of the site access process.

Breath alcohol testing devices compliant with AS 3547:2019, including portable units for on-site reasonable-suspicion checks and fixed-point screening solutions for high-volume entry points, are the appropriate alcohol testing method in these contexts.

Building a Testing Program That Matches the Obligation

The four areas covered in this article are interconnected components of a single obligation: a principal contractor who manages and controls a construction site is responsible for managing impairment risk across everyone who works on it.

A testing program that matches this obligation combines a current, legally reviewed site drug and alcohol policy, pre-access and ongoing oral fluid testing that covers the full site workforce, SWMS-integrated impairment management for HRCW activities, breath alcohol testing at appropriate trigger points and result documentation that creates an auditable compliance record across all contractors and testing events.

Regulatory scrutiny of construction site impairment risk is increasing, particularly in jurisdictions where recent WHS prosecutions have examined the adequacy of principal contractor oversight across the full subcontractor chain. Principal contractors who build a comprehensive testing program now are positioning their operations to meet a standard that is moving toward being expected rather than exceptional.

Speak with the Andatech team about drug and alcohol testing for your construction site

Andatech supplies oral fluid drug test kits, breath alcohol testing devices and cloud-based result management solutions used by construction businesses across Australia. Contact the team to discuss pre-access testing protocols, AS/NZS 4760:2019-compliant saliva testing and audit-ready result management for multi-contractor sites.