n-Pentane Storage & Tank Compatibility

Storing n-Pentane? Start Here

n-Pentane (C₅H₁₂, CAS 109-66-0) is a clear, colorless, extremely volatile straight-chain alkane used as a low-boiling laboratory and process solvent, a blowing agent for foam, and a component of light naphtha and gasoline blendstocks. With a boiling point near 97 F and a flash point around -57 F, it flashes and evaporates readily at ambient conditions, and its vapors are heavier than air and travel to distant ignition sources. As a non-polar hydrocarbon it dissolves oils, waxes and resins but is practically insoluble in water and floats on it. For tank and containment selection the controlling facts are its extreme flammability and its tendency to swell and permeate polyethylene, so n-pentane is handled in grounded metal or fluoropolymer-lined equipment rather than in polyethylene tanks.

Is n-Pentane Compatible With Polyethylene (HDPE / XLPE) Tanks?

No. n-Pentane is not compatible with polyethylene. Like other light aliphatic hydrocarbons, pentane is absorbed by HDPE and crosslinked polyethylene (XLPE), causing the wall to swell, soften and lose strength while the solvent permeates through it over time. Plastic resistance charts consistently rate polyethylene as not recommended for hydrocarbon solvents in this carbon-number range. Even where short-term contact appears tolerable, permeation creates a flammable-vapor hazard outside the tank and progressive dimensional change in the wall. Store and transfer n-pentane in grounded, bonded carbon or stainless steel vessels, or in fluoropolymer-lined equipment, with FKM (Viton) elastomers. Polyethylene, polypropylene and PVC should all be avoided for liquid pentane service.

Material compatibility at a glance

n-Pentane is a light, volatile, non-polar aliphatic hydrocarbon. It is incompatible with polyethylene (HDPE and XLPE), polypropylene and PVC, which swell, soften and are permeated by hydrocarbon solvents. Suitable materials of construction are properly grounded and bonded carbon or stainless steel with fluoropolymer (PTFE/PFA) linings and FKM (Viton) seals. Because of the extreme flammability and very low flash point, electrostatic and ignition-source control govern equipment selection.

Ratings: S suitable · C conditional / limited · U unsuitable. Verify against the cited resistance charts and your concentration/temperature before specifying.

The safety that actually matters

• Extremely flammable (NFPA flammability 4): vapor forms explosive mixtures with air and can flash back from distant ignition sources. Eliminate open flames, sparks and hot surfaces.
• Bond and ground all containers, pumps and transfer lines; the low conductivity of pentane lets static charge accumulate and ignite vapor during transfer.
• Store in a cool, well-ventilated, detached or fire-rated area away from oxidizers; keep below the flash point is not practical, so rely on inerting and ventilation.
• May be fatal if swallowed and enters the airways (aspiration hazard, H304); never siphon by mouth and prevent ingestion.
• Vapor causes respiratory irritation, drowsiness and dizziness (H335, H336); use local exhaust ventilation and a supplied-air or organic-vapor respirator as required.
• Toxic to aquatic life (H401, H411); contain spills and prevent release to drains, soil and surface water.

Common questions

Can I store n-pentane in a poly (HDPE or XLPE) tank?

No. Light aliphatic hydrocarbons such as n-pentane swell, soften and permeate polyethylene. Use grounded carbon or stainless steel, or fluoropolymer-lined equipment, with FKM (Viton) seals.

What is the NFPA 704 rating for n-pentane?

Health 1, Flammability 4, Instability 0, per CAMEO Chemicals and the PubChem safety summary. The flammability 4 reflects its very low flash point of about -57 F and high volatility.

Why is n-pentane such a serious fire hazard?

Its flash point is roughly -57 F and its vapor pressure is high, so it produces ignitable vapor well below room temperature. The vapor is heavier than air and can travel to a remote ignition source and flash back, so static control, bonding and grounding are essential.

What materials are compatible with n-pentane?

Carbon and stainless steel, PTFE/PFA fluoropolymers, and FKM (Viton) elastomers are suitable. Polyethylene, polypropylene, PVC and EPDM are not recommended because hydrocarbons swell and permeate them.