Kerosene is a blend of liquid hydrocarbons, molecules built almost entirely from carbon and hydrogen atoms, with carbon chains typically ranging from about 12 to 15 carbon atoms long.1PubMed. Study of Determination of Oil Mixture Components Content Based on Quasi-Monte Carlo Method It is not a single chemical compound but a mixture of hundreds of individual molecules drawn from several distinct hydrocarbon families. The exact proportions shift depending on the crude oil source and the refining process, which is why jet fuel, lamp oil, and rocket-grade kerosene can all carry the “kerosene” label yet behave quite differently.
The Main Hydrocarbon Families
When chemists analyze a kerosene sample, they sort the individual molecules into a handful of structural families. A detailed analytical method for doing this groups kerosene compounds into paraffins (both straight-chain and branched), naphthenes (ring-shaped saturated hydrocarbons), and aromatics (molecules containing at least one benzene-like ring).2Fuel. PIONA analysis of kerosene by comprehensive two-dimensional gas chromatography coupled to time of flight mass spectrometry A large study of 70 jet fuel samples further broke aromatics down into simple aromatic compounds, naphthalene-derived compounds, and tetralin- and indane-derived compounds, confirming that the aromatic fraction alone is chemically diverse.3Processes. Chemical Composition and Low-Temperature Fluidity Properties of Jet Fuels
Straight-chain paraffins (sometimes called normal paraffins or n-alkanes) are the simplest members. Picture a chain of carbon atoms in a line, each one bonded to hydrogen atoms along the way. Branched paraffins, or isoparaffins, have the same formula but with side branches jutting off the main chain. Together, these paraffins usually make up the largest share of a typical kerosene sample, and they contribute most of its energy content per unit weight.
Naphthenes are ring-shaped molecules, often with five or six carbon atoms forming the ring, sometimes with short side chains attached. They tend to be denser than paraffins and have slightly different combustion characteristics. Aromatics, meanwhile, contain flat ring structures with alternating double bonds. A small aromatic fraction helps with certain performance properties, like seal-swelling in fuel system gaskets, but too much raises soot formation and smoke output. Jet fuel specifications typically cap the aromatic content at around 20 to 25 percent by volume for exactly this reason.
Why No Two Batches Are Identical
Because kerosene is distilled from crude oil, its composition reflects the crude it came from. A light, sweet crude from one region might yield kerosene heavy in straight-chain paraffins, while a heavier, more aromatic crude from another region produces kerosene with a larger naphthenic and aromatic fraction. Even within a single refinery, the kerosene fraction collected on different days can vary as the crude oil feedstock changes.
This variability matters for researchers who need to model kerosene’s behavior, especially its combustion. Since tracking hundreds of individual molecules is impractical, they create “surrogate fuels” that mimic the real thing using just a handful of representative compounds. One surrogate developed for RP-3, a Chinese rocket-grade kerosene, uses a mix of five compounds: n-dodecane, n-decane, isohexadecane, methylcyclohexane, and toluene.4Fuel. A new reduced reaction mechanism of the surrogate fuel for RP-3 kerosene Another modeling effort chose just n-decane as a stand-in for the entire kerosene mixture, because n-decane captures many of kerosene’s combustion properties reasonably well on its own.5PubMed Central. Chemical kinetic simulation of kerosene combustion in an individual flame tube The fact that a single ten-carbon-chain molecule can roughly approximate the combustion behavior of hundreds of compounds tells you something about how dominant the paraffin fraction really is.
How Kerosene Gets Refined
Kerosene begins as crude oil pumped from underground reservoirs. At a refinery, the crude enters a distillation column, a tall tower where the oil is heated and its components separate by boiling point. Lighter molecules like those in gasoline boil off and rise to the top. Heavier ones destined for diesel and fuel oil stay near the bottom. Kerosene occupies a middle range, typically collected between roughly 150°C and 275°C. This “cut” captures molecules in the C10 to C16 range, though the heart of the fraction clusters around C12 to C15.
Raw kerosene straight off the distillation column still contains impurities, especially sulfur compounds. Refineries remove sulfur through a process called hydrodesulfurization, which uses hydrogen gas and a metal catalyst to break apart carbon-sulfur bonds and pull the sulfur out as hydrogen sulfide gas.6ScienceDirect. Design and optimization of hydrodesulfurization process for liquefied petroleum gases Reducing sulfur content matters for both engine performance and emissions: sulfur compounds corrode metal parts and produce sulfur dioxide when burned, which contributes to acid rain and particulate formation.
Additional refining steps can include hydrotreating to remove nitrogen compounds and trace metals, and sometimes a clay treatment or chemical wash to improve color and stability. The depth of refining depends on the end use. Household lamp oil, for instance, undergoes heavier processing to reduce smoke and odor, while industrial heating kerosene may receive only minimal treatment.
Jet Fuel, Lamp Oil, and Rocket Kerosene
The word “kerosene” covers a surprisingly wide range of products. Household kerosene, sometimes sold as paraffin oil or K-1, is refined for clean burning in portable heaters and lamps. Jet A and Jet A-1 are aviation-grade kerosenes with tighter specifications on freezing point, thermal stability, and energy density. The main difference between Jet A and Jet A-1 is their freezing point: Jet A freezes at about −40°C, while Jet A-1 must remain liquid down to −47°C, a requirement driven by the extremely cold temperatures at high altitude on long-haul flights.
These aviation fuels also carry chemical additives that household kerosene typically does not. Anti-icing additives, for example, prevent ice crystals from forming in fuel lines at altitude. These additives are glycol-based compounds that dissolve in any water droplets present in the fuel, lowering the freezing point of that water. Research into these compounds has also shown that some of them have biocidal properties, meaning they can kill microorganisms that would otherwise grow in fuel tanks.7PubMed Central. Biocidal properties of anti-icing additives for aircraft fuels Microbial growth in fuel tanks is a genuine maintenance concern for airlines, because bacteria and fungi feed on hydrocarbons and produce acidic byproducts that corrode tank linings.
Other common jet fuel additives include antioxidants to prevent gum and sediment from building up during storage, corrosion inhibitors to protect metal surfaces, static dissipator additives to prevent electrostatic charge buildup during fueling, and thermal stability improvers. None of these additives changes the fundamental hydrocarbon makeup of the kerosene. They are present in tiny concentrations, usually parts per million, and serve as performance-enhancing extras layered on top of the base fuel.
Military-grade kerosenes like JP-8 have their own additive packages and specifications tuned for battlefield logistics. Rocket-grade kerosenes such as RP-1 (used by American launch vehicles) and RP-3 (used in Chinese aerospace) are refined to even tighter standards, with strict limits on sulfur, olefins, and aromatic content. These fuels need to be extremely predictable in their combustion behavior, because even small composition shifts can affect engine performance in ways that matter when you are putting a payload into orbit.
What Happens When Kerosene Burns
In an idealized world, burning kerosene would produce only carbon dioxide and water. The reality is messier. Incomplete combustion generates carbon monoxide, unburned hydrocarbons, and soot. The aromatic fraction is especially prone to producing soot, because those stable ring structures resist full oxidation and instead polymerize into tiny carbon particles.
Among the more concerning combustion byproducts are polycyclic aromatic hydrocarbons, or PAHs. These are multi-ring aromatic molecules, some of which are known carcinogens. Research analyzing soot from kerosene flames has confirmed that PAHs are detectable in the particulate matter produced by burning kerosene, whether the source is a conventional petroleum kerosene or a bio-derived alternative.8PubMed. Determination of polycyclic aromatic hydrocarbons in kerosene and bio-kerosene soot This finding is relevant to the roughly three billion people worldwide who still use kerosene lamps and stoves for lighting and cooking, particularly in low-income households without access to electricity or cleaner fuels.
The combustion chemistry itself involves hundreds of intermediate reactions. When modelers simulate kerosene combustion, they track the stepwise breakdown of long-chain hydrocarbons into progressively smaller fragments: first into medium-chain radicals, then into molecules with two or three carbon atoms, and finally into carbon monoxide and carbon dioxide.4Fuel. A new reduced reaction mechanism of the surrogate fuel for RP-3 kerosene Even a “reduced” combustion model for kerosene involves over a hundred chemical species and hundreds of reactions. The full chemistry is far more complex, but for practical engineering purposes, these reduced models predict ignition timing, flame speed, and emissions well enough to design engines around.
Health Risks From Kerosene Exposure
Kerosene’s chemical makeup creates several pathways for harm. The hydrocarbons in kerosene are lipophilic, meaning they dissolve readily in fats and oils, including the natural lipids in your skin, lungs, and cell membranes. A review of kerosene toxicity found that major affected systems include the lungs, central nervous system, cardiovascular system, skin, immune system, and liver.9PubMed. Effects and mechanisms of kerosene use-related toxicity The mechanisms behind these effects are varied: kerosene vapor can trigger inflammation in the airways, strip away the natural surfactant that keeps lung tissue pliable, generate reactive oxygen species that damage cells, and suppress immune function.
Skin contact is one of the most common exposure routes. Because kerosene dissolves the lipids that hold the outer skin layer together, repeated or prolonged contact leads to drying, cracking, and irritation. Workers who handle kerosene regularly, including aircraft maintenance crews, are particularly exposed. A toxicity study on a synthetic kerosene (an alcohol-to-jet fuel called SB-8) found that the fuel was moderately irritating to skin under fully covered conditions but only slightly irritating when the skin could breathe.10PubMed. Toxicity and human health assessment of an alcohol-to-jet (ATJ) synthetic kerosene developed under an international agreement with Sweden That distinction matters in practice: spills trapped under gloves or clothing are more harmful than brief incidental contact.
The same study tested inhaled exposure in rats over 90 days and found that at the highest exposure level, some animals developed mild lung tissue changes, including increased numbers of immune cells in the airways and small patches of cell overgrowth in the air sacs. Neurobehavioral changes were subtle, limited to increased activity and decreased grooming in females at the highest dose. These findings were comparable to those reported for conventional petroleum-derived JP-8 fuel, suggesting that the hydrocarbon composition, whether petroleum-sourced or synthetically produced, drives similar biological effects.10PubMed. Toxicity and human health assessment of an alcohol-to-jet (ATJ) synthetic kerosene developed under an international agreement with Sweden
Accidental ingestion is perhaps the most dangerous acute exposure, particularly in children. Swallowed kerosene can be aspirated into the lungs during vomiting, causing chemical pneumonitis, a severe inflammatory reaction. This is why medical guidance strongly discourages inducing vomiting after kerosene ingestion; the aspiration risk during vomiting is often worse than the kerosene sitting in the stomach.
What Happens When Kerosene Reaches Soil or Water
Kerosene spills are an environmental concern wherever fuel is stored, transported, or used. Because kerosene is a complex mixture, its components degrade at different rates. Lighter, straight-chain paraffins tend to evaporate or get broken down by soil bacteria relatively quickly, while heavier branched and aromatic compounds persist longer.
The good news is that kerosene is biodegradable. Bacteria that naturally live in soil can use kerosene hydrocarbons as a food source. One study isolated bacteria from hydrocarbon-contaminated sites and found that some strains could degrade up to 91% of the kerosene in a laboratory medium within 15 days.11PubMed Central. Kerosene Biodegradation by Highly Efficient Indigenous Bacteria Isolated From Hydrocarbon-Contaminated Sites Lab conditions are more favorable than real-world soil, but field studies confirm that biodegradation does occur in practice, especially when nutrients like nitrogen and phosphorus are available. In one soil study, adding nutrients boosted kerosene degradation from about 27% to 65% over six weeks.12International Biodeterioration & Biodegradation. Biodegradation of kerosene in soil by a mixed bacterial culture under different nutrient conditions
Extreme environments tell a different story. In high-arctic intertidal sediment, researchers found that most of the kerosene added to experimental plots, around 94 to 98%, was lost from the upper sediment layer within just two days, primarily through evaporation and physical dispersal rather than biological breakdown.13PubMed. Persistence and biodegradation of kerosene in high-arctic intertidal sediment A residual fraction stubbornly clung to the sediment. When a bioremediation agent was added, it actually increased initial retention (because it kept the kerosene in contact with the sediment rather than letting it wash away), but it also stimulated a massive bloom of hydrocarbon-degrading bacteria. Even so, biological degradation accounted for only about 17% of the subsequent kerosene removal. In cold environments with limited microbial activity, physical processes dominate and the aromatic and branched components can persist for extended periods.
Synthetic and Bio-Derived Kerosene
Petroleum is not the only possible starting material for kerosene-range hydrocarbons. Synthetic kerosenes can be produced from natural gas (through Fischer-Tropsch synthesis), from alcohols derived from plant sugars (the alcohol-to-jet pathway), or from hydroprocessed plant oils and animal fats. The end products are tuned to fall within the same carbon-number range and meet the same physical specifications as petroleum kerosene, but their hydrocarbon profiles differ in characteristic ways.
Fischer-Tropsch kerosene, for instance, is almost entirely paraffinic. It contains very few aromatics and virtually no sulfur, which means it burns cleaner and produces less soot. The downside is that trace aromatics actually serve a function in conventional jet fuel: they cause slight swelling of the elastomer seals in fuel systems, keeping them tight. A fuel with zero aromatics can cause those seals to shrink and leak. This is why synthetic paraffinic kerosenes are typically approved for use only as blends with conventional petroleum-derived jet fuel, usually up to 50% of the total.
Hydroprocessed esters and fatty acids (HEFA) kerosene, made from plant oils or used cooking oil, also skews heavily paraffinic. It tends to have excellent cold-flow properties and low sulfur, but like Fischer-Tropsch fuel, it needs blending. The alcohol-to-jet route can produce a somewhat broader range of hydrocarbon types depending on the process conditions. As the toxicity study mentioned earlier confirmed, these synthetic fuels produce similar biological effects to petroleum kerosene at comparable exposure levels, reinforcing the idea that it is the hydrocarbon chemistry itself, not the feedstock origin, that determines how kerosene interacts with living tissue.
Trace Components and Impurities
Beyond the dominant carbon-and-hydrogen hydrocarbons, kerosene contains small amounts of compounds incorporating sulfur, nitrogen, and oxygen. These heteroatom compounds, as chemists call them, typically make up a small percentage of the total by weight, but they punch above their weight in terms of practical impact.
Sulfur compounds are the most scrutinized. They corrode engine parts, poison catalysts in emission-control systems, and produce sulfur oxides when burned. Jet fuel specifications typically set an upper limit of around 0.3% sulfur by mass, and refiners use hydrodesulfurization to get below that threshold.6ScienceDirect. Design and optimization of hydrodesulfurization process for liquefied petroleum gases Household kerosene intended for indoor use is often refined to even lower sulfur levels to reduce the smell and fumes.
Nitrogen compounds, while present in smaller quantities, can contribute to deposit formation and instability during long-term storage. Oxygen-containing compounds, such as naphthenic acids, can promote corrosion and emulsion problems when water is present. None of these trace impurities change the fundamental identity of kerosene as a hydrocarbon mixture, but they explain why refining goes well beyond simple distillation and why different grades of kerosene carry different price tags. The chemistry you pay for in premium kerosene is less about what was added and more about what was taken away.