ISO 22262-1 Evaluation Method: Assessment of Rubber Fume in Workplace Atmospheres

ISO 22262-1 defines a standardized evaluation method for measuring rubber fume in workplace atmospheres, combining inhalable dust sampling with solvent extraction and gravimetric analysis. This technical article explains the scope of the standard, the sampling and testing procedures, typical applications in the rubber processing industry, and answers to frequently asked questions.

Technical Overview

ISO 22262-1 is the first part of the ISO 22262 series, which addresses the evaluation of rubber fumes in occupational environments. The standard specifies a method for sampling and analyzing airborne rubber fume generated during rubber processing operations such as mixing, extrusion, calendering, and vulcanization. Because rubber fume consists of a complex mixture of particulate matter and condensable organic compounds, the standard defines an operational measurement approach rather than targeting a single chemical substance.

The core principle of the ISO 22262-1 evaluation method is the collection of the inhalable fraction of airborne particulate on a suitable filter medium using a personal or static sampler, followed by solvent extraction of the collected material and gravimetric determination of the soluble organic fraction. This approach has a long history in occupational hygiene practice, as the solvent-soluble fraction of rubber fume serves as a practical surrogate indicator of overall fume exposure in rubber manufacturing facilities.

The method supports comparison of measured airborne concentrations against occupational exposure limits and internal company benchmarks, and provides a defensible, reproducible basis for exposure assessment programs.

Testing Samples

Workplace Air Samples from Rubber Processing Areas

The primary sample type is filter-deposited particulate collected from the breathing zone of workers or from fixed locations in production areas. Personal sampling in the breathing zone is preferred for exposure assessment, while static (area) sampling is useful for evaluating background concentrations and source contributions.

Filters and Filter Deposits

Low-background filter media compatible with solvent extraction, such as glass fiber or membrane filters, are used to collect the inhalable particulate fraction. The filter must be conditioned and weighed before sampling to establish a reliable tare mass, and the collected deposit must remain intact during transport to the laboratory.

Field and Laboratory Blanks

Field blanks, which travel with the sample filters but are not used for sampling, and laboratory blanks are essential quality control elements. They allow correction for filter mass instability, contamination during handling, and solvent or laboratory background contributions.

Testing Items

The ISO 22262-1 evaluation method typically covers the following measurement parameters:

• Airborne concentration of the solvent-soluble organic fraction of rubber fume, expressed in milligrams per cubic meter of air sampled.
• Total collected particulate mass on the filter, which may be determined gravimetrically to characterize the total inhalable dust burden.
• Blank-corrected soluble fraction, obtained by applying field and laboratory blank corrections to the extracted mass.
• Extraction efficiency and recovery verification, using quality control checks to confirm that the solvent extraction step performs acceptably.
• Sampling volume verification, based on recorded flow rates and sampling duration, to convert measured mass into an airborne concentration.

Testing Methods

The evaluation procedure under ISO 22262-1 follows a defined sequence of sampling, extraction, and gravimetric determination:

• Sample collection: An inhalable fraction sampler fitted with a pre-weighed filter is attached to the worker or positioned at a fixed location. Sampling is performed at a controlled, documented flow rate, commonly covering a full work shift so that the result reflects a time-weighted average exposure.
• Pre- and post-sampling handling: Filters are conditioned in a controlled temperature and humidity environment before weighing to minimize mass drift. After sampling, filters are returned to the laboratory in protective cassettes together with field blanks.
• Solvent extraction: The filter deposit is extracted with a suitable organic solvent, typically cyclohexane in established rubber fume practice, using techniques such as Soxhlet extraction or validated ultrasonic extraction. The solvent dissolves the organic, fume-derived fraction of the collected particulate.
• Gravimetric determination: The mass of the insoluble residue retained after extraction is determined by microbalance, and the solvent-soluble fraction is obtained by difference from the total collected mass. Alternatively, the extracted solution may be evaporated and the residue weighed directly, according to the validated laboratory procedure.
• Calculation and reporting: The airborne concentration of the soluble fraction is calculated by dividing the blank-corrected soluble mass by the volume of air sampled. Results are reported with the sampling duration, flow rate, extraction method, and analytical uncertainty.

Laboratories performing this evaluation should operate under a documented quality management system, use calibrated sampling pumps and balances, and participate in interlaboratory comparisons where available.

Applications

The ISO 22262-1 evaluation method is applied across the rubber and polymer processing industries wherever fume exposure may occur:

• Tire manufacturing, including mixing, extrusion, calendering, and curing lines where elevated fume levels are historically associated with hot processing steps.
• General rubber goods production, such as molded and extruded technical rubber components, seals, hoses, and belts.
• Latex and rubber compounding facilities, where process dust and fume require combined exposure assessment.
• Occupational health surveillance programs, providing time-weighted average exposure data for epidemiological and compliance purposes.
• Engineering control validation, used to verify the effectiveness of local exhaust ventilation, enclosure, and process modification measures by comparing concentrations before and after intervention.
• Regulatory compliance demonstration, supporting employers in demonstrating that workplace exposures are maintained below applicable occupational exposure limits or internal action levels.

FAQ

What does ISO 22262-1 measure?

The standard measures the airborne concentration of rubber fume in workplace atmospheres, expressed operationally as the solvent-soluble organic fraction of collected inhalable particulate. It is a marker measurement of overall fume exposure rather than an analysis of individual chemical species.

Why is the solvent-soluble fraction used as the indicator?

Rubber fume is a chemically complex mixture containing hundreds of organic compounds. The solvent-soluble fraction provides a practical, reproducible, and historically established surrogate that correlates with the organic, fume-derived portion of the airborne particulate.

How long should sampling be conducted?

Sampling is typically performed over a full work shift to obtain a time-weighted average concentration representative of daily exposure. Shorter-duration sampling may be used for task-specific or engineering control studies when documented appropriately.

How do results differ from a total inhalable dust measurement?

Total inhalable dust measurement captures all airborne particulate regardless of origin, including non-rubber dust. The ISO 22262-1 approach isolates the solvent-soluble organic portion, which more specifically reflects rubber fume contribution in processing areas.

How should results be interpreted?

Measured concentrations should be compared against applicable occupational exposure limits, company action levels, and historical data from the same facility. Interpretation should account for sampling uncertainty, process conditions, and the operational nature of the surrogate measurement.