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The Complete Guide to
ASHRAE 110 Fume Hood
Performance Testing
Everything lab managers, safety officers, and procurement teams need to know about the ASHRAE 110 fume hood performance test standard — in plain language.
What Is ASHRAE 110?
ANSI/ASHRAE Standard 110-2016 (R2025) — commonly shortened to ASHRAE 110 — is the authoritative American National Standard for testing the containment performance of laboratory fume hoods. Jointly developed by the American National Standards Institute (ANSI) and the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), it has governed fume hood evaluation since its first publication in 1985, with major revisions in 1995 and 2016, and was reaffirmed again in 2025.
The standard provides a structured set of quantitative and qualitative test procedures to answer one fundamental question: can this fume hood reliably contain and exhaust hazardous vapors under representative operating conditions?
Quick definition: The full name of the current standard is ANSI/ASHRAE 110-2016 (R2025): Methods of Testing Performance of Laboratory Fume Hoods. When manufacturers advertise a hood as "ASHRAE 110 certified," they are claiming it passed one or more of these structured test protocols.
Why ASHRAE 110 Matters for Your Lab
Fume hoods are the single most important engineering control in chemical laboratories. OSHA's Occupational Exposure to Hazardous Chemicals standard (29 CFR 1910.1450) mandates that engineering controls — including fume hoods — must be the primary means of reducing employee exposure to toxic substances. It also requires that these devices be confirmed to function correctly.
This is precisely where the ASHRAE 110 fume hood performance test standard serves a critical role: it gives labs, safety officers, and regulators a common, reproducible language to verify that a hood actually performs as designed.
- 1Regulatory compliance OSHA 29 CFR 1910.1450 and ANSI/AIHA Z9.5 both point to ASHRAE 110 as the benchmark for fume hood validation.
- 2Objective performance data Rather than relying on manufacturer claims alone, ASHRAE 110 produces quantifiable, comparable numbers — parts per million of tracer gas, exact face velocity readings — enabling real apples-to-apples comparisons between suppliers.
- 3Early problem detection Periodic ASHRAE 110 testing catches deteriorating seals, failing baffles, or HVAC changes before they become safety incidents.
- 4Insurance & institutional requirements Universities, pharmaceutical companies, and government labs frequently require proof of ASHRAE 110 compliance as a condition of operation or funding.
The 3 Core Tests in the ASHRAE 110 Standard
The ASHRAE 110 fume hood performance test standard organizes its evaluation around three distinct procedures, each targeting a different aspect of hood behavior. All three are typically required for a complete assessment.
Test 1 — Face Velocity Measurement
Measures the average inflow speed of air across the hood's open face using a calibrated thermal anemometer. Readings are taken at multiple grid points, one per second for 20 seconds, then averaged. For VAV hoods, measurements are taken at 25%, 50%, and full sash openings.
Test 2 — Smoke Visualization
A qualitative test using titanium tetrachloride (TiCl₄) sticks or a theatrical smoke machine. Evaluators watch whether smoke is cleanly captured and directed toward the baffles — or whether turbulence near the sash causes any visible escape. Both small-volume and large-volume smoke tests may be performed.
Test 3 — Tracer Gas Containment
The most rigorous test. Sulfur hexafluoride (SF₆) gas is released inside the hood at 4.0 liters per minute. A probe placed in the mannequin's breathing zone feeds an analyzer that logs SF₆ concentration every second. The 5-minute average determines whether the hood passes.
A closer look at the tracer gas test
The tracer gas containment test is considered the gold standard within ASHRAE 110 because it simulates real-world exposure risk more accurately than smoke or airflow measurements alone. A full-size mannequin represents the lab technician; the detection probe sits at nose height. The hood interior contains an SF₆ ejector positioned at standardized locations to challenge the most vulnerable areas of containment.
SF₆ is used because it is chemically inert, non-toxic at test concentrations, heavier than air (mimicking many lab solvents), and detectable at concentrations as low as 0.01 ppm — making it extremely sensitive to even minor containment failures.
Environmental note: SF₆ is a potent greenhouse gas. Some testing agencies are now validating nitrous oxide (N₂O) as an alternative tracer gas that delivers equivalent sensitivity with a dramatically lower carbon footprint — a shift that may be reflected in future revisions of the standard.
AM, AI & AU — Three Test Scenarios
ASHRAE 110 doesn't just define what to measure — it also defines when and under what conditions to measure it. The standard recognizes three distinct test scenarios, each capturing a different stage of a fume hood's lifecycle.
| Scenario | Full Name | Where Tested | Purpose | Status |
|---|---|---|---|---|
| AM | As Manufactured | Factory / manufacturer's lab | Confirms the hood meets design specifications under ideal controlled conditions before shipment | Required |
| AI | As Installed | On-site, after full installation | Validates that real-world HVAC connections, room cross-drafts, and building conditions do not degrade performance | Required |
| AU | As Used | On-site, with equipment inside | Evaluates containment under realistic working conditions — with instruments, containers, and obstructions present inside the hood | Recommended |
Key insight: A fume hood can pass the AM test in the factory and still underperform once installed, because room conditions — supply air diffuser placement, cross-drafts from HVAC, foot traffic patterns — significantly influence containment. This is why AI testing in the actual laboratory is just as important as the manufacturer's factory certification.
Pass Criteria & Performance Rating
One of the most common questions lab buyers ask is: what does it actually take to pass? Here is a practical summary of the key thresholds defined within the ASHRAE 110 fume hood performance test standard.
| Test | Metric | Pass Threshold | Notes |
|---|---|---|---|
| Face Velocity | Average inflow velocity | Typically 75–100 fpm (0.38–0.51 m/s) | Exact target varies by institution and applicable local code. Uniformity across grid points also assessed. |
| Smoke Visualization | Visual containment | No visible smoke escaping the hood face or sash perimeter | Qualitative; observer assesses flow patterns and turbulence near critical zones. |
| Tracer Gas | 5-min avg SF₆ at breathing zone | ≤ 0.05 ppm | Lower is better. Many high-performance hoods achieve 0.01–0.02 ppm. Readings above threshold = fail. |
What "AM 0.05" means on a data sheet
When you see a notation like "AM 0.05" on a manufacturer's specification sheet, it means the hood was tested As Manufactured and the average tracer gas reading in the breathing zone was 0.05 ppm — the threshold of a passing score. The best certified hoods will often show readings of 0.01 ppm or 0.02 ppm AM, indicating substantially better containment performance than the minimum required. When comparing suppliers, a lower AM value represents a meaningfully safer product.
Important nuance: ASHRAE 110 is a performance test method, not a safety specification. The standard explicitly notes that tracer gas readings do not translate directly to actual operator chemical exposure levels. Treat it as a comparative benchmark rather than an absolute safety guarantee — and pair it with appropriate chemical hygiene plans and PPE.
ASHRAE 110-1995 vs. 2016: What Changed?
The 2016 revision was the most significant update to the standard since 1995. If you have older test certificates or are evaluating legacy equipment, understanding the key differences matters.
| Area | ASHRAE 110-1995 | ASHRAE 110-2016 (current) |
|---|---|---|
| Data collection | Manual recording permitted | Required Digital/electronic data capture only |
| Face velocity instrument | Various anemometers allowed | Thermal anemometer with integration capability required to reduce instantaneous reading errors |
| VAV testing | Limited guidance | Full procedure: 25%, 50%, and 100% sash positions for variable air volume systems |
| Information sections | Brief | Significantly expanded background, installation guidance, and cross-draft evaluation sections |
| Diagrams | Basic | Comprehensive diagrams of correctly tested hood configurations |
The 2016 version was reaffirmed without changes in 2025, confirming that the current edition remains the active standard for the foreseeable future.
Which Fume Hoods Does ASHRAE 110 Cover?
The standard explicitly covers four types of laboratory fume hoods. Understanding which category your hood falls into affects how it is tested and what performance expectations apply.
Conventional Hoods
Standard constant-air-volume (CAV) hoods with a fixed exhaust rate. The most widely used type in laboratories worldwide; simplest to test under ASHRAE 110.
Bypass Hoods
Include a bypass opening that maintains airflow when the sash is closed, preventing pressure surges. Testing must account for bypass behavior at different sash positions.
Auxiliary Air Hoods
Use an additional external supply air stream at or near the face to reduce conditioned air exhaust. Testing verifies that the auxiliary air curtain does not disrupt containment.
Variable Air Volume (VAV)
Modulate exhaust airflow based on sash position or occupancy sensors — the most energy-efficient option. ASHRAE 110-2016 introduced full three-position testing protocols specifically for VAV systems.
Not covered: Ductless recirculating hoods, biological safety cabinets (covered by NSF/ANSI 49), and perchloric acid hoods require separate evaluation criteria and are outside the scope of ASHRAE 110.
Buying a Certified ASHRAE 110 Fume Hood
When your procurement team is evaluating lab fume hoods, the ASHRAE 110 test certificate is one of the most telling documents a supplier can provide. Here is what to look for — and what to ask — before placing an order.
- 1Request the actual test report, not just a claim A reputable manufacturer will provide the full ASHRAE 110 test data sheet, including the exact AM tracer gas value (e.g., "AM 0.01 ppm"), test date, hood model, and sash configuration tested. A certificate without the underlying data offers little assurance.
- 2Confirm testing was done on your specific model ASHRAE 110 results apply to a specific hood model and size. A test performed on a 1200 mm wide hood does not automatically validate a 1800 mm version of the same design.
- 3Check whether the test covers VAV operation If your lab uses a variable air volume system, ensure the AM test report includes results at all three sash positions (25%, 50%, 100%). A report showing only full-open testing may not reflect performance at partially closed sash positions.
- 4Plan for AI testing at installation Budget for on-site ASHRAE 110 AI testing as part of your lab setup costs. Even a perfectly manufactured hood can underperform if lab air supply, HVAC balance, or room layout introduces cross-drafts above 50% of face velocity.
- 5Schedule annual retesting OSHA and ANSI/AIHA Z9.5 both recommend periodic testing at minimum once per year. Build this into your lab's preventive maintenance schedule from day one.
Looking for an ASHRAE 110-Certified Fume Hood?
Explore our metal chemical fume hood range — factory-tested to ASHRAE 110 standards, available in multiple widths and sash configurations.
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