If you operate a fixed-roof tank that stores a flammable or combustible liquid, a flame arrester (sometimes spelled flame arrestor) is not a nice-to-have. It is the passive barrier that stops an external ignition source – a lightning strike, a hot surface, or a static discharge – from flashing back into your tank’s vapour space and igniting the whole contents. This guide gives you the chemical storage tank flame arrester requirements you must meet, the flame arrester standard set that applies, and a practical flame arrester selection framework you can hand straight to your engineering team.
QUICK ANSWER
For a typical atmospheric chemical storage tank you need an end-of-line (EOL) flame arrester on the vent nozzle, selected to the tank’s gas group (MESG), operating pressure and temperature, and vapour flow, and built to ISO 16852 with API 2000 vent sizing. Pair it with a breather valve with an integrated flame arrester so pressure relief and flashback protection work together.
Every fixed-roof tank breathes. Solar heating pushes vapour out; cooling and pump-out pull air back in. That vent path is also the route a flame would travel to reach your stored liquid. A flame arrester sits in that path and quenches the flame front by absorbing heat through its metal element, dropping the gas below its auto-ignition temperature before it can enter the tank. For you, that means the difference between a routine vent and a tank-loss incident.
Most operators specify one because a code or a client demands it – but even where it is not strictly mandated, the cost of a single flashback event (personnel risk, lost product, shutdown, reputational damage) dwarfs the price of the device. If your tank holds a flammable or combustible liquid and sits where an ignition source is plausible, the tank flame arrester requirements are effectively non-negotiable.
You choose the type from where the flame can form and how fast it can travel. For storage tanks the decision is usually simple, but knowing the three families stops you from overspecifying.
Mounted on the open end of a vent nozzle, an End-of-Line (EOL) flame arrester blocks an external ignition source from entering. It is the default for atmospheric tank vents, breather-valve outlets, and gauge-hatch openings, because the flame path is short and the threat is outside-in.
Used inside piping where a subsonic (deflagration) flame could propagate – vapour-recovery lines, tank-to-tank manifolds, loading arms. They quench a flame that is already inside the pipe before it reaches the tank or a neighbouring vessel.
Required only where a pipe run is long enough for a deflagration to accelerate to a supersonic detonation. For a normal storage tank vent this is rarely needed, so specifying it adds cost and certification burden you do not have to carry.
When you write a specification, you are really writing a list of standards. The flame arrester standard set below is what your supplier must answer to – and what an inspector will check.
| Standard | What it covers | What it means for you |
|---|---|---|
| API 2000 | Vent sizing for atmospheric and low-pressure storage tanks | Sets the vapour flow your API 2000 flame arrester and breather valve must pass |
| ISO 16852 | Flame arrester performance and testing | The core product standard – always require a third-party test report |
| ATEX / IECEx | Explosive-atmosphere certification (EU / international) | Needed for EU and many MENA / Asian projects |
| ASME B6528 | US flame arrester standard | Required for US chemical and petrochemical plants |
| NFPA 30 / 69 | Flammable liquids and explosion protection | Defines when protection is mandated for your occupancy |
Your flame arrester selection comes down to five inputs. Miss any one and you either undersize (a safety gap) or oversize (wasted budget).
The element gap must be smaller than the Maximum Experimental Safe Gap (MESG) of your vapour. Match the group, not the product name:
| Gas group | Example vapours | MESG (mm) | Arrester class |
|---|---|---|---|
| IIA | Propane, butane, gasoline, methanol | >0.9 | Standard EOL / in-line |
| IIB | Ethylene, ethanol, town gas | 0.5 – 0.9 | Tighter element |
| IIC | Hydrogen, acetylene | ≤0.5 | Special foil element, certified |
Take the maximum operating pressure and temperature from your tank data, then the peak vapour flow from your API 2000 calculation. The arrester’s rated flow must exceed that peak with margin – a common rule is 20% headroom so the device never runs at its limit.
Stainless steel is the default for chemical service; 304 suits most solvents, 316L resists chlorides and acids. For aggressive or low-temperature duty, check the corrosion chart before you commit. Our ZCZHQ-II stainless steel flame arresters cover the IIA/IIB range in 304 and 316L bodies with ANSI flanges.
Not sure of your gas group, MESG, or peak vapour flow? Send us your tank data and our engineers will return an exact model and size recommendation.
Browse Our Flame ArrestersA flame arrester is not free to flow – its element adds pressure drop. Size it from the same API 2000 vapour flow you used for the breather valve, and confirm the combined pressure drop stays well inside the tank’s mechanical limits. If the arrester chokes the vent, you have only moved the risk from fire to vacuum collapse. For the worked math, see our API 2000 tank vent sizing guide. Match the arrester’s DN and flange class to the existing nozzle so you are not re-nozzling the roof.
On most tanks the arrester and the breather valve sit in the same vent line. You can buy them as separate items stacked on the nozzle, or as one combined unit. A combined breather valve with an integrated flame arrester saves height, removes a flange joint, and guarantees the two are sized for the same flow. Size the arrester for the valve’s rated capacity so neither becomes the bottleneck.
Install the EOL unit vertically at the vent outlet, element horizontal, with clear access for inspection. Keep the inlet path short and unobstructed. Flame arresters are passive, but they are not fit-and-forget: a clogged or corroded element raises pressure drop and can fail closed exactly when you need it open. Plan a yearly external inspection, a documented cleaning schedule, and recertification against ISO 16852 at the interval your supplier specifies. Keep the records – they are what an auditor asks for first.
A flame arrester quenches a propagating flame front with a fine metal element sized to the gas MESG, stopping flashback into the tank. A spark arrester only traps solid burning particles (sparks, embers) in an exhaust stream and will not stop a gas-phase flame. For a flammable vapour space you need a flame arrester, not a spark arrester.
It depends on your jurisdiction and occupancy, but the direction is clear: API 2000, NFPA 30, and OSHA process-safety expectations all push flammable-liquid storage toward vent protection. Even where a local code stops short of mandating it, insurers and major clients routinely require it in writing. Treat it as required unless a documented risk assessment says otherwise.
On an end-of-line vent, a single EOL arrester protects the nozzle regardless of flow direction, so it covers both outbreathing and inbreathing. If you separate the pressure and vacuum paths (for example through a PVRV with distinct seats), confirm each opening that can see an ignition source carries its own protection.
It adds some drop, which is why you size it from the same API 2000 flow as the breather valve and keep the combined drop inside the tank’s mechanical limits. A correctly selected arrester passes the peak vapour flow with margin; a poorly selected one becomes the bottleneck. The fix is sizing, not omission.
Watch for rising pressure drop versus the as-new baseline, visible corrosion or pitting on the element, embedded coke or polymer fouling that will not clear, and any mechanical damage to the housing or gasket. Any of these means the unit should be cleaned, re-certified, or replaced before it is relied on in a fire case.
An EOL arrester goes at the top of the vent outlet, generally vertically with the element plane horizontal, so condensate cannot pond in the element and so it is reachable for inspection. Keep the upstream piping short and direct, and follow the manufacturer’s minimum straight-run and access requirements – do not bury it behind a valve you cannot isolate.
– API 2000 Calculation: Step-by-Step Tank Vent Sizing Guide – the formulas, factor tables, and a worked example (read this before you size).
– Breather Valve Sizing and Venting Capacity – turning a required flow into an orifice and set pressure.
– Breather Valve vs. Emergency Vent – when your tank needs both devices.
– Flame Arrester Product Category – the full ZhenChao range.
This guide is prepared by ZhenChao (Zhejiang Zhenchao Petrochemical Equipment Co., Ltd.), a tank-protection equipment manufacturer founded in 2006 with 18+ years of field experience. Our flame arresters and breather valves are supplied to storage and process projects across the Middle East, Central Asia, and beyond, built to ISO and ATEX requirements, and backed by factory-direct engineering support. The content is reviewed by our application engineers against API 2000, ISO 16852, and ASME B6528. For certified capacity, MESG class, and material data, contact our team for the specification sheet.
Let’s specify your tank flame arrester correctly – the first time.
Send your tank data – liquid, gas group, pressure, temperature, and flow – and our engineers will return an exact model, size, and quote.
Read the API 2000 Sizing Guide
