Rethinking the 8-mm rule: Why HVE bore size alone may not define effective aerosol control

For years, many dental professionals have accepted an old standard stating that high-volume evacuation (HVE) devices must have a bore size of 8 millimeters or greater to be considered effective for aerosol removal. This guideline is often referenced as a hard requirement, yet its scientific basis is far less robust than many assume. In an era that prioritizes efficient infection control, ergonomics, and hands-free solutions, it may be time to reexamine whether an 8-mm diameter is truly the defining factor in aerosol capture—or whether relying on bore size alone oversimplifies a much more complex system. 

Why diameter became the default metric 

Historically, an 8-mm internal opening served as a convenient shorthand: Large enough to allow substantial airflow, easy to identify visually, and aligned with the capabilities of traditional vacuum systems. But diameter is only a proxy for potential airflow. It says nothing about actual volumetric flow at the tip, internal turbulence, shape, design, or how a device performs when it’s actually used in the human mouth. 

Modern manufacturers producing smaller-bore evacuation attachments have demonstrated that design and engineering can offset, and sometimes outperform, larger diameters. Smooth internal surfaces, optimized intake geometry, aerodynamics that guide airflow efficiently, and minimized resistance throughout the system can all significantly influence real-world performance. In other words, bigger is not automatically better when it comes to aerosol capture. 

The hands-free factor: Where new designs shift the equation 

A major limitation of the traditional 8-mm rule is that it assumes the HVE tip is actively held, correctly positioned, and consistently maintained at the aerosol source. Clinically, this is rarely the case. 

A key advantage of advanced HVE attachments is their hands-free functionality. Unlike handheld devices, which are often not used continuously throughout an entire procedure or may drift from the ideal position, these innovative devices maintain a stable, uninterrupted seal at the source of aerosol production. Continuous suction equals more consistent containment. This alone addresses one of the greatest weaknesses of traditional HVE: operator variability. 

Most traditional HVE devices are not hands free. When a clinician or assistant must choose between holding the suction tip or performing a task, suction often becomes intermittent or suboptimally positioned. Even a large-diameter device cannot compensate for improper or inconsistent placement. Newer, hands-free designs remove this variable entirely. 

What the research shows 

A 2022 study by Teichert-Filho et al. compared aerosol-reducing devices and confirmed that while HVE significantly reduces aerosol levels, hands-free systems demonstrated slightly lower efficacy when the aerosol source was moved around the oral cavity. This finding highlights the role of device placement and technique rather than bore size alone.¹ 

Additionally, a 2021 study by Koletsi et al. similarly found that devices like ReLeaf and DryShield performed effectively but showed variability depending on how the aerosol-generating instrument was repositioned.² 

Notably, neither study concluded that smaller-bore or hands-free devices were ineffective—only that performance fluctuated when placement changed. With continuous suction and consistent positioning, hands-free systems maintain aerosol capture without relying on continuous operator attention. These findings argue strongly that technique and positioning influence aerosol reduction more than bore diameter. 

Toward performance-based standards, not diameter-based rules 

If the goal is true aerosol mitigation, the question should not be “Is the bore 8 mm?” but rather the following: 

• What volumetric flow rate (L/min) does the device deliver at the tip? 

• How effectively does the device capture aerosols across clinically relevant particle sizes? 

• How consistently can it maintain positioning throughout an entire procedure? 

• Does the design reduce operator fatigue, improve ergonomics, or allow hands-free function? 

Conclusion 

Measurable, repeatable, clinically meaningful performance-based standards are far more relevant than an outdated dimensional requirement. The longstanding 8-mm HVE rule is rooted more in tradition than in modern evidence. Bore size affects airflow, but it is far from the only determinant of aerosol capture. Hands-free solutions offer continuous suction, consistent positioning, ergonomic advantages, and design efficiencies that challenge the assumption that “larger is automatically more effective.” 

As dentistry continues evolving toward evidence-based infection control, it’s time to reconsider the oversimplified 8-mm benchmark and embrace performance metrics that reflect how evacuation devices actually function in the clinical environment. 

Editor's note: This article appeared in the March 2026 print edition of RDH magazine. Dental hygienists in North America are eligible for a complimentary print subscription. Sign up here.

References 

1. Piela K, Watson P, Donnelly R, et al. Aerosol reduction efficacy of different intra-oral suction devices during ultrasonic scaling and high-speed handpiece use. BMC Oral Health. 2022;22(1):388. doi:10.1186/s12903-022-02386-w 

2. Comisi JC, Ravenel TD, Kelly A, et al. Aerosol and spatter mitigation in dentistry: analysis of the effectiveness of 13 setups. J Esthet Restor Dent. 2021;33(3):466-479. doi:10.1111/jerd.12717