Cigarette tar content testing and analysis quantifies the machine-measured yields of nicotine-free dry particulate matter (tar), together with nicotine, water, and carbon monoxide, in mainstream cigarette smoke. Using internationally recognized ISO smoking standards and their GB/T national equivalents, accredited third-party laboratories deliver reproducible emission data that supports regulatory compliance, product development, and quality control. This article explains the sample types, analytical workflow, calculation principles, and typical applications of professional tar content determination.
Technical Overview
Tar is the collective term for the particulate-phase condensate of cigarette smoke, formally defined in analytical practice as nicotine-free dry particulate matter (NFDPM). It is not measured directly; instead, the total particulate matter (TPM) trapped on a glass-fiber filter pad during machine smoking is weighed, and the water and nicotine fractions within that condensate are determined chemically. Tar is then obtained by calculation: tar equals TPM minus water minus nicotine.
The determination is performed with a routine analytical smoking machine that draws puffs from cigarettes under strictly standardized conditions. Because machine yields depend entirely on how the cigarette is smoked, international standards such as ISO 4387 and its Chinese equivalent GB/T 19609 prescribe every parameter of the process, from laboratory atmosphere to puff profile. This standardization allows tar values to be compared between laboratories, between production lots, and against regulatory ceilings.
- Tar is reported in milligrams per cigarette, typically rounded to 0.1 mg.
- Modern commercial products generally yield in the range of 1 mg to 10 mg per cigarette under the ISO regimen.
- Tar, nicotine, and carbon monoxide are conventionally reported together as the core smoke emission set.
- Machine-measured yields characterize product emissions under fixed conditions and do not directly measure human exposure.
Testing Samples
Finished Cigarettes
The standard sample is the finished cigarette in its marketed configuration, including king-size, slim, and superslim formats, regular and recessed filters, menthol and capsule variants, and paper or composite tipping. The product is tested exactly as sold, since filter ventilation, rod density, and paper permeability all strongly influence tar delivery.
Semi-Finished Products and Other Formats
Cigarette rods, uncut filter assemblies, and roll-your-own tobacco filled into standard tubes can also be evaluated using adapted procedures, for example during process development or incoming material control. For non-standard geometries, the laboratory adjusts parameters such as butt length while keeping the puff conditions unchanged, and the deviations are documented in the report.
Sample Quantity and Integrity
A complete determination normally requires a minimum of 100 to 200 cigarettes to cover replicate smoking runs, physical pre-screening, and retention. Packs must be received unopened and undamaged, and obviously defective cigarettes, for example those with loose tow, torn paper, or missing filters, are excluded during sampling. Samples are marked in advance for butt-length control before they enter the smoking machine.
Testing Items
A routine tar content examination comprises a defined package of measurands, each expressed on a per-cigarette basis:
- Total particulate matter (TPM), determined gravimetrically, in mg per cigarette.
- Water in the smoke condensate, determined by gas chromatography, in mg per cigarette.
- Nicotine in the smoke condensate, determined by gas chromatography, in mg per cigarette.
- Tar (nicotine-free dry particulate matter), calculated as TPM minus water minus nicotine, in mg per cigarette.
- Carbon monoxide in the vapor phase, determined by non-dispersive infrared analysis, in mg per cigarette.
- Number of puffs per cigarette and residual butt length.
- Filter ventilation, measured according to ISO 9512 and reported as a percentage where relevant to interpretation.
Testing Methods
Sampling and Atmospheric Conditioning
Samples are drawn from production or market lots by statistical sampling in accordance with ISO 8243 or GB/T 5606.1. Before smoking, cigarettes are conditioned for at least 48 hours in the standard tobacco laboratory atmosphere of 22 °C ± 2 °C and 60 % ± 5 % relative humidity, as specified in ISO 3402 and GB/T 16447. Conditioning equilibrium is essential because moisture in the tobacco affects burn rate and therefore all smoke yields.
Machine Smoking under Standard ISO Conditions
Smoking is carried out on a linear or rotary analytical smoking machine conforming to ISO 3308. The ISO regimen specifies a puff volume of 35 mL, a puff duration of 2 seconds, one puff every 60 seconds, and a bell-shaped puff flow profile. Cigarettes are smoked to a defined butt length, normally the filter overwrap length plus 3 mm or 23 mm, whichever is greater. Mainstream smoke is drawn through a pre-conditioned 44 mm Cambridge filter pad, which retains the particulate phase while the vapor phase passes onward for gas analysis. A typical determination consists of at least five replicate smoking channels of 20 cigarettes each.
Gravimetric Determination of Total Particulate Matter
Filter pads are equilibrated in the laboratory atmosphere and weighed to 0.1 mg before and after smoking. Blank pads are handled in parallel to correct for environmental moisture uptake. TPM per cigarette is the corrected pad mass gain divided by the number of cigarettes smoked on that channel.
Gas Chromatographic Determination of Water and Nicotine
The smoked pads are extracted with a suitable solvent containing internal standards. Water in the extract is quantified by gas chromatography in line with ISO 10362-1, and nicotine by gas chromatography with flame ionization or nitrogen-phosphorus detection in line with ISO 10315, using the corresponding GB/T national methods. Multi-level calibration curves and certified reference materials verify the response of each system.
Determination of Carbon Monoxide
The vapor phase passing through the pad is collected, and carbon monoxide is measured by non-dispersive infrared analyzers according to ISO 8454 and its GB/T equivalent. The analyzers are calibrated with certified carbon monoxide gas mixtures, and the measured volume concentration is converted to mg per cigarette using the puff count and puff volume.
Calculation and Reporting of Tar
Tar is calculated as NFDPM per cigarette equals TPM per cigarette minus water per cigarette minus nicotine per cigarette. Reports state the smoking regimen, puff count, per-cigarette yields of tar, nicotine, and carbon monoxide, and any deviations from the standard method. Values are normally rounded to 0.1 mg per cigarette.
Intense and Alternative Smoking Regimens
Besides the ISO regimen, laboratories can apply intense regimens such as the Health Canada Intense condition, which uses a 55 mL puff volume, a 2 second duration, one puff every 30 seconds, and complete blocking of filter ventilation holes. Intense data are required in several jurisdictions for emission notification and provide a complementary, more demanding characterization of the same product. Results from different regimens must never be mixed in comparison.
Quality Assurance of the Determination
Reliable tar data depend on rigorous quality control: regular verification of puff volume, puff duration, and pressure drop of the smoking machine; gravimetric and chromatographic calibration checks; environmental monitoring of the smoking room; control charts on reference cigarettes; and participation in interlaboratory proficiency programs. Testing performed by ISO/IEC 17025-accredited third-party laboratories provides independent assurance of data quality.
Applications
Tar content testing is a cornerstone measurement across the entire tobacco product life cycle, serving regulatory, industrial, and scientific purposes:
- Regulatory compliance: verifying that machine-measured tar yields meet emission ceilings, such as the 10 mg per cigarette limit applicable in China and the ceilings historically enforced in the European Union under Directive 2001/37/EC.
- Emission notification: supplying ISO and intense-regimen data required for product registration and reporting under frameworks such as the EU Tobacco Products Directive and WHO FCTC obligations.
- Product research and development: quantifying how blend composition, filter length, ventilation, and paper permeability affect delivery when designing lower-yield products.
- Manufacturing quality control: monitoring lot-to-lot consistency and releasing production batches against internal tar specifications.
- Market surveillance and trade: checking imported or sampled products against declared values and national limits.
- Scientific research: providing the baseline emission data on which toxicology studies and broader smoke chemistry investigations are built.
It should be emphasized that machine-measured tar is a standardized product characteristic, not a measure of what any individual smoker absorbs. WHO guidance cautions against using ISO numbers alone to infer differences in risk between products, which is why accredited laboratories report the regimen and full emission set alongside the tar value.
FAQ
What exactly is tar in a cigarette test report?
Tar is the nicotine-free dry particulate matter of mainstream smoke, obtained by subtracting the water and nicotine content from the total particulate matter collected on the Cambridge filter pad. It is a calculated result expressed in mg per cigarette.
Why not measure tar directly?
The particulate condensate contains a large fraction of water and nicotine by mass. International standards therefore define tar as the corrected, dry, nicotine-free residue so that values are comparable across products and laboratories.
Which standards govern the analysis?
The core methods are ISO 8243 for sampling, ISO 3402 for conditioning, ISO 3308 for the smoking machine, ISO 4387 for TPM and NFDPM, ISO 10362-1 for water, ISO 10315 for nicotine, and ISO 8454 for carbon monoxide. In China, the equivalent GB/T series, including GB/T 19609, GB/T 23355, GB/T 23356, and GB/T 16447, applies.
How many cigarettes are needed?
A routine ISO determination uses at least 100 cigarettes, typically five replicates of 20, plus reserves for screening and retests. Intense-regimen testing follows the same replication logic.
Why do ISO and intense results differ so much?
The intense regimen uses a larger, more frequent puff and blocks filter ventilation, driving more tobacco consumption and higher yields. Both results describe the same product under different fixed smoking conditions, and each is valid only within its own regimen.
How precise are the results?
With calibrated equipment, controlled atmosphere, and proper replication, repeatability limits specified in ISO 4387 are typically met, and experienced laboratories achieve relative repeatability within a few percent for tar. Measurement uncertainty should be stated when values are close to regulatory thresholds.