Methyl acetate (CAS 79-20-9; EC 201-185-2; CH₃COOCH₃; relative molecular mass 74.08 g/mol) is a volatile acetate ester solvent with transport classification UN 1231, Class 3, Packing Group II. In Safety Data Sheet Section 2, the substance carries harmonized GHS codes H225, H319, and H336, with supplemental statement EUH066 under Annex II of Regulation (EC) No 1272/2008. The signal word is Danger, and the label pictograms are GHS02 and GHS07. Methyl Acetate SDS & GHS Hazard Codes Decoded: H225 indicates highly flammable liquid and vapour; H319 indicates causes serious eye irritation; H336 indicates may cause drowsiness or dizziness; and EUH066 indicates repeated exposure may cause skin dryness or cracking.

Physical data supporting the flammable classification include a closed-cup flash point of -10 °C, a boiling point of 56.9 °C at 101.3 kPa, a vapour pressure of 22.7 kPa at 20 °C, and a relative vapour density of 2.55 relative to air. The lower explosive limit is 3.1 vol%, the upper explosive limit is 16.0 vol%, and the autoignition temperature is 454 °C. At 20 °C, the saturated vapour concentration is approximately 224,000 ppm, which exceeds the upper explosive limit in an unventilated closed headspace, but dilution during venting or sampling inevitably passes through the flammable range. The vapour density greater than 1.0 causes released vapour to accumulate in low points, pits, and floor drains.

What Does H225 Mandate for Hazardous Area Classification and Storage Containment?

Under NFPA 30, methyl acetate falls within Class IB flammable liquid parameters because the flash point is below 22.8 °C and the boiling point is at or above 37.8 °C. Hazardous area classification following EN 60079-10-1:2021 places process areas with routine vapour release into Zone 1 or Zone 2 depending on ventilation reliability. Electrical equipment in such zones is selected for gas group IIA and temperature class T1, because the autoignition temperature of 454 °C exceeds the T1 surface-temperature ceiling of 450 °C. Static discharge is controlled through bonding and grounding; NFPA 77 recommends a resistance to ground of less than 10 Ω for conductive process equipment. Transfer lines constructed of non-conductive polymer must not be used without a continuous static dissipative path. Storage vessels are fitted with pressure-vacuum vents and, where local regulation requires, flame arrestors to prevent external flashback. Nitrogen blanketing may be applied to maintain the vapour space outside the flammable range when the process requires extended storage at ambient temperature.

Eye irritation classification H319 is assigned because direct contact with liquid or high vapour concentration produces corneal and conjunctival injury that is reversible but clinically significant. SDS Section 11 references ocular irritation testing under OECD Test Guideline 405; the substance is not classified as corrosive to the eye. At large-scale transfer stations, closed-loop sampling and dry-break couplings reduce the probability of splash exposure. Emergency eyewash equipment conforming to ANSI/ISEA Z358.1 must deliver tepid flushing fluid for at least 15 minutes in areas where a credible eye-contact scenario exists. Eye protection selected under EN 166:2001 includes chemical-splash goggles or a face shield worn over safety glasses. If contact occurs, SDS Section 4 instructs immediate irrigation with water, removal of contact lenses, and continuation of irrigation while medical evaluation is arranged. The absence of a corrosive classification does not eliminate the requirement for secondary eye-protection enforcement because methyl acetate rapidly penetrates thin ocular tear film and generates local methanolic and acetic acid hydrolysis products.

Occupational Exposure Thresholds Linking H336 and EUH066 to Ventilation Rates

SDS Section 8 for methyl acetate commonly references the OSHA Permissible Exposure Limit of 200 ppm as an 8-hour time-weighted average and the NIOSH Recommended Exposure Limit of 200 ppm with a short-term exposure limit of 250 ppm. ACGIH has assigned a TLV-TWA of 200 ppm and a TLV-STEL of 250 ppm, with the basis including eye and upper respiratory irritation. The OSHA PEL is listed in 29 CFR 1910.1000 Table Z-1 as 200 ppm and 610 mg/m³. The NIOSH IDLH value is 3,100 ppm, derived as 10% of the lower explosive limit. The H336 classification reflects transient central nervous system depression at vapour concentrations substantially above occupational exposure limits, not a specific chronic target-organ effect. Saturated vapour concentration at 20 °C is 224,000 ppm, approximately 1,120 times the OSHA PEL, so an open vessel in a small enclosure can generate narcosis-relevant concentrations before the lower explosive limit is reached if ventilation is inadequate.

EUH066 is not a GHS hazard class under the UN Globally Harmonized System; it is an EU CLP supplemental statement addressing repeated dermal exposure. Methyl acetate defats the stratum corneum through lipid extraction, producing dryness and cracking that may be accompanied by fissuring at the fingertips or knuckles. Skin protection selection uses chemical permeation data under EN 16523-1:2015+A1:2018 or ASTM F739-20. Thin single-use nitrile gloves are not appropriate for immersion or prolonged wet contact unless the manufacturer reports a breakthrough time acceptable for the task. Multi-layer laminate or fluoropolymer barrier gloves are generally preferred for production-scale operations involving methyl acetate. Workers must wash exposed skin after handling, and contaminated clothing should be removed because it retains vapour and can prolong skin contact. SDS Section 8 should specify glove material and thickness based on the task, not solely on generic chemical resistance tables.

If Methyl Acetate Is Unloaded from Road Tankers into Ambient Storage

Tanker transfer of methyl acetate occurs under UN 1231, Class 3, Packing Group II. Receiving tanks should be located in an impervious bund with capacity not less than 110% of the largest container. Closed-loop vapour return between tanker and storage vessel reduces holdup vapor release. Liquid velocity should be limited during initial fill to avoid static charge accumulation; conventional guidance for non-conductive hydrocarbon-like esters uses a fill velocity not exceeding 1 m/s until the inlet is submerged. Pumps and level instruments located in the unloading area must be rated for the classified zone and the autoignition temperature class. Overfill prevention systems should include independent high-level and high-high-level interlocks. Flexible hoses are conductive or static-dissipative, inspected for cracking and delamination before each transfer campaign, and tagged according to a periodic test programme.

Small containers of methyl acetate are stored in approved flammable liquid cabinets or dedicated solvent rooms. Larger drums and intermediate bulk containers require continuous ventilation, explosion-group-compatible electrical installation, and separation from oxidizers, strong acids, and strong bases. Sources of ignition are excluded from storage areas, and the SDS Section 7 statement “keep away from heat, hot surfaces, sparks, open flames and other ignition sources” is implemented through permit-to-work systems. The NFPA 704 rating is Health 1, Flammability 3, Instability 0. Fire suppression for small to moderate storage rooms may include dry chemical or carbon dioxide systems, while alcohol-resistant aqueous film-forming foam is used by trained fire brigades for larger tanker and storage fire response under NFPA 11.

Hydrolytic Decomposition Modifies Fire and Corrosion Boundaries in Moisture-Rich Storage

Methyl acetate is subject to hydrolysis in the presence of water and catalytic amounts of acid or base, producing methanol and acetic acid. This hydrolysis pathway alters SDS Section 10 stability data where moisture intrusion is possible. The acetic acid by-product can depress pH and accelerate corrosion of carbon steel storage and transfer equipment. Therefore, carbon steel tanks handling methyl acetate with water contamination require periodic bottom-water draw-off and pH monitoring. Stainless steel 316L and PTFE-lined equipment are common for low-moisture closed systems where product purity must be preserved. Published compatibility data for specific elastomer compounds are limited; gasket and seal selection should be confirmed by immersion testing at the expected operating temperature and water cut. Methyl acetate may also extract plasticizers from flexible thermoplastics, producing seal shrinkage and leakage if the wrong polymer is used.

Spill response for methyl acetate requires vapour exclusion and drainage protection. Small spills are absorbed with inorganic absorbent or vermiculite and placed in closed conductive containers. Dry sweeping with non-conductive brushes is unacceptable because of static discharge risk. Larger spills require vapour-impermeable sumps, explosion-proof pumps, and exclusion of all ignition sources within the vapour-dispersion distance. Direct water spray may spread the liquid and should be avoided except for cooling containers or dispersing vapour under controlled conditions. Fire suppression run-off must be diked and disposed as hazardous waste; methyl acetate is not suitable for sewer discharge. In fire situations, vapours may travel to distant ignition sources and flash back, so unignited vapour plumes are treated as explosive atmospheres until upper explosive limit readings are confirmed below the lower flammable limit.