Cigarette tar determination is a standardized laboratory procedure for measuring the nicotine-free dry particulate matter (NFDPM) in mainstream smoke, a key figure printed on every pack and required by tobacco regulators worldwide. This article explains the complete testing protocol based on ISO 4387, ISO 3308, ISO 10315, ISO 10362, and the Chinese national standard GB/T 19609, covering sample conditioning, machine-smoking parameters, condensate analysis, and result calculation. It serves as a practical technical reference for quality engineers, laboratory analysts, and compliance specialists working in accredited third-party laboratories or in-house tobacco testing facilities.
Technical Overview
Tar, formally defined as nicotine-free dry particulate matter (NFDPM), is the water- and nicotine-free fraction of the total particulate matter (TPM) retained when mainstream cigarette smoke is generated under strictly controlled machine-smoking conditions. Because tar cannot be measured directly, it is obtained by difference: the smoke condensate collected on a glass-fiber filter pad is weighed to give TPM, and the water and nicotine contents of that condensate are determined analytically and then subtracted.
The internationally recognized procedure is specified in ISO 4387, which is adopted in China as the national standard GB/T 19609. A family of supporting standards defines the complete measurement chain, from conditioning atmosphere to chromatographic analysis of the condensate:
- ISO 4387 / GB/T 19609 — determination of TPM and NFDPM (tar) using a routine analytical smoking machine
- ISO 3308 — definitions and standard conditions for the routine analytical smoking machine
- ISO 3402 — conditioning and testing atmospheres for tobacco and tobacco products
- ISO 10315 — determination of nicotine in smoke condensates by gas chromatography
- ISO 10362-1 and ISO 10362-2 — determination of water in smoke condensates by gas chromatography or Karl Fischer titration
- ISO 8454 — determination of carbon monoxide in the vapor phase, frequently measured alongside tar for labeling purposes
Testing Samples
Finished Cigarette Products
Commercial king-size and slim filtered cigarettes are the most frequently tested sample type. Samples are drawn from production batches or retail packages in accordance with an established sampling plan, and unopened packs are conditioned intact until analysis. Both filter and non-filter cigarette formats can be tested, with the butt length adjusted according to the product configuration.
Reference and Monitor Cigarettes
Certified reference cigarettes with assigned TPM, water, nicotine, and tar values are smoked at defined intervals as method-control samples. Consistent recovery of the certified values confirms that the smoking machine, analytical instruments, and operator technique remain under statistical control.
Prototype and Experimental Products
Development samples such as new blend formulations, modified filter designs, altered paper permeability, or laser-perforated ventilation variants are tested to quantify how design changes influence delivery. These samples may be limited in quantity, so the test plan is adapted while preserving the minimum replicate requirements of the standard.
Testing Items
A complete determination yields the following parameters, each expressed in milligrams per cigarette:
- Total particulate matter (TPM), mg/cigarette
- Water content of the smoke condensate, mg/cigarette
- Nicotine content of the smoke condensate, mg/cigarette
- Tar (NFDPM), calculated as TPM minus water minus nicotine, mg/cigarette
- Average puff count per cigarette
- Optionally, carbon monoxide in the vapor phase, mg/cigarette, to obtain the tar–nicotine–CO triple used for mandatory pack labeling
Testing Methods
Sample Conditioning and Preparation
Cigarettes are conditioned in a climate room at 22 °C ± 2 °C and 60 % ± 5 % relative humidity for a minimum of 48 hours, in accordance with ISO 3402. After conditioning, test cigarettes are visually inspected and any specimens with physical defects are excluded. If statistical selection is applied, cigarettes are weighed and only those falling within a documented mass band around the mean are retained, so that the tested set represents the population. The butt length for each cigarette is marked before loading.
Standard Machine-Smoking Conditions
Samples are smoked on a linear or rotary analytical smoking machine operated under the standard ISO 3308 regimen:
- Puff volume: 35 mL, with a permissible deviation of no more than 0.3 mL per puff
- Puff duration: 2.0 seconds, within a tolerance of 0.05 seconds
- Puff interval: one puff every 60 seconds, within a tolerance of 0.5 seconds
- Puff flow profile: bell-shaped, as specified for routine analytical machines
- Butt length: for filter cigarettes, the tipping-paper overwrap length plus 3 mm, and never shorter than 23 mm
- Smoking laboratory atmosphere maintained at 22 °C ± 2 °C and 60 % ± 5 % relative humidity
- A minimum of 20 cigarettes per determination, distributed across replicate collection channels
Collection and Gravimetric Determination of TPM
A pre-conditioned, pre-weighed 44 mm Cambridge glass-fiber filter pad is installed in each cigarette holder. The assigned cigarettes are smoked to the marked butt length, the puff counter is recorded, and the holder assembly is reweighed on an analytical balance. TPM equals the mass gain of the holder assembly divided by the number of cigarettes smoked. The spent pad is inspected for uniform smoke staining; edge streaking, breakthrough, or pad overload invalidates the channel. Any cigarette that extinguishes during the run is recorded, and the affected channel is rejected and repeated.
Determination of Water and Nicotine in the Condensate
The Cambridge filter pad is transferred to an extraction vessel and shaken with a measured volume of isopropanol containing suitable internal standards. The extract is analyzed on two chromatographic systems:
- Water is determined by gas chromatography with thermal-conductivity detection, or alternatively by Karl Fischer titration, following ISO 10362
- Nicotine is determined by gas chromatography with flame-ionization detection, following ISO 10315
Both instruments are calibrated with certified reference solutions, and blank pad extracts are analyzed to confirm negligible background. Results are converted to milligrams per cigarette.
Calculation and Reporting
Tar is obtained by difference from the three measured values: Tar (NFDPM) = TPM − Water − Nicotine, with all terms in mg/cigarette. The replicate channel results are averaged, checked against the precision criteria of ISO 4387, and reported rounded to the nearest 0.1 mg per cigarette together with the mean puff count, smoking conditions, and butt length. Out-of-control channels, such as those with verified puff-volume deviations or irregular pad deposition, are excluded and re-tested.
Equipment Calibration and Quality Control
- Verification of puff volume, duration, and interval before each test series using a calibrated volume-measuring device
- Leak testing of the puffing circuit and confirmation of acceptable pressure-drop characteristics
- Regular calibration of analytical balances, ovens, and chromatographic systems with traceable references
- Periodic smoking of certified reference cigarettes and maintenance of control charts for TPM, water, nicotine, and tar
- Documented environmental monitoring of the smoking laboratory temperature and humidity
Applications
- Regulatory compliance testing and mandatory disclosure of tar, nicotine, and CO yields on cigarette packaging
- Verification of conformance to maximum tar ceilings imposed in certain markets
- Product development, including blend optimization, filter design, and ventilation engineering
- Manufacturing quality control, batch release, and stability monitoring
- Comparative benchmarking of commercial products and support of scientific or regulatory research on smoke chemistry
FAQ
What exactly is "tar" in a cigarette?
Tar is the nicotine-free dry particulate matter collected from mainstream smoke on a Cambridge filter pad under standard machine-smoking conditions, after subtracting the water and nicotine contained in that condensate. It is a laboratory-defined analytical quantity rather than a single chemical substance.
Why are water and nicotine subtracted from TPM?
Total particulate matter includes water and nicotine, which are measured separately and reported independently. Removing them yields a dry, nicotine-free residue that provides a consistent basis for comparing deliveries across products and over time.
What are the standard ISO smoking parameters?
The standard regimen is a 35 mL puff of 2.0 seconds duration taken once every 60 seconds until the cigarette is smoked to the specified butt length. These conditions, defined in ISO 3308, must be verified on every smoking run.
How many cigarettes are required for one determination?
A minimum of 20 conditioned cigarettes is typically required, distributed across replicate collection channels so that channel-to-channel variability can be assessed and a meaningful average delivery calculated.
How does the ISO regimen differ from intense smoking regimens?
Intense regimens use a larger puff volume (commonly 55 mL), a shorter puff interval (commonly 30 seconds), and, in some protocols, complete blocking of filter ventilation. They generate higher deliveries and are used for supplementary characterization, whereas the ISO regimen remains the basis for standard labeling values.
What precision can be expected?
ISO 4387 specifies repeatability and reproducibility limits for TPM and NFDPM. Well-controlled laboratories using calibrated linear or rotary smoking machines and validated chromatographic methods routinely achieve repeatability within these limits, and participation in interlaboratory comparisons is recommended to demonstrate ongoing competence.