The Gastec 91P Formaldehyde Detector Tubes are designed for sensitive, low-level measurement of formaldehyde (HCHO) in air using a compatible automatic air sampling pump.

The 91P provides a quantitative measuring range of 0.02 to 1.44 ppm, with a detection limit of 0.01 ppm under the specified sampling conditions. The tube produces a yellow-to-pink color change for visual determination of formaldehyde concentration.

Each box contains 10 detector tubes for 10 tests.

IMPORTANT STORAGE REQUIREMENT: Gastec 91P detector tubes have a 12-month shelf life when stored refrigerated. Follow the storage conditions printed on the detector tube packaging.

Automatic Air Sampling Pump Required

IMPORTANT: Gastec 91P Formaldehyde Detector Tubes require a compatible automatic air sampling pump capable of maintaining a continuous 200 mL/min sampling rate.

Compatible Pump: Gastec GSP-501FT Automatic Air Sampling Pump

The 91P is an automatic air sampling pump detector tube and should not be treated as a standard hand-pump detector tube. Accurate measurement depends on maintaining the specified sampling rate, sampling time, and total sample volume.

Do not substitute a standard manual Gastec detector tube pump for the required automatic sampling method.

Measurement & Sampling Specifications

Measurement Range	Sampling Rate	Sample Volume	Correction Factor	Sampling Time
0.02–0.4 ppm	200 mL/min	6,000 mL	1	30 Minutes
0.4–1.44 ppm	200 mL/min	2,000 mL	3.6	10 Minutes

For measurements from 0.02 to 0.4 ppm, sample at 200 mL/min for 30 minutes, providing a total sample volume of 6,000 mL. The correction factor is 1.

For measurements above 0.4 ppm and up to 1.44 ppm, use a fresh detector tube and sample at 200 mL/min for 10 minutes, providing a total sample volume of 2,000 mL. Multiply the detector tube reading by the specified 3.6 correction factor.

Product Specifications

Brand: Gastec
Tube Type: Formaldehyde Detector Tube for Automatic Air Sampling Pump
Part Number: 91P
Gas Measured: Formaldehyde (HCHO)
Measurement Range: 0.02–1.44 ppm
Primary Measurement Range: 0.02–0.4 ppm
Extended Measurement Range: 0.4–1.44 ppm
Detection Limit: 0.01 ppm at 6,000 mL (minimum detectable concentration; not part of the quantitative measuring range)
Sampling Rate: 200 mL/min
Primary Sample Volume: 6,000 mL
Extended-Range Sample Volume: 2,000 mL
Correction Factor: 1 or 3.6 depending on measurement range
Primary Sampling Time: 30 Minutes
Extended-Range Sampling Time: 10 Minutes
Color Change: Yellow → Pink
Operating Temperature: 5–35°C (41–95°F), temperature correction required
Operating Humidity: 20–90% RH, humidity correction not required
Relative Standard Deviation: 10% for 0.02–0.1 ppm; 5% for 0.1–0.4 ppm
Quantity: 10 Tubes
Tests per Box: 10 Tests
Shelf Life: 12 Months When Refrigerated
Storage: Refrigerated
Pump Requirement: Compatible Automatic Air Sampling Pump Required

Low-Level Formaldehyde Measurement

The Gastec 91P is designed for sensitive measurement of formaldehyde (HCHO) in environmental atmospheric conditions.

Its quantitative measuring range extends from 0.02 to 1.44 ppm using two sampling procedures.

For low-level measurements from 0.02–0.4 ppm, the longer 30-minute sampling period and 6,000 mL total sample volume provide the conditions necessary for quantitative measurement.

The 0.01 ppm detection limit represents the minimum concentration capable of producing a detectable reaction under the specified 6,000 mL sampling conditions. It is not part of the quantitative measuring range and should not be interpreted as a 0.01–1.44 ppm measuring range.

During sampling, formaldehyde reacts with the reagent in the detector tube and produces a visible yellow-to-pink color change.

Common Applications

Gastec 91P Formaldehyde Detector Tubes may be used for applicable low-level formaldehyde air monitoring applications including:

• Indoor Air Quality Testing

• Residential Environment Monitoring

• Workplace & Industrial Hygiene Monitoring

• Building & Facility Air Quality Investigations

• Formaldehyde Emission Investigations

• Chemical & Manufacturing Environments

• Laboratory & Research Applications

• Environmental Atmospheric Monitoring

• Furniture, Building Material & Product Emission Investigations

• Low-Level Formaldehyde Monitoring

Temperature Correction

The Gastec 91P is designed for use between 5 and 35°C (41–95°F) and requires temperature correction.

Gastec provides a temperature correction table in the official 91P instruction manual. Determine the concentration indicated by the detector tube and apply the appropriate temperature correction according to the actual sampling temperature.

The specified relative humidity range is 20–90% RH, and humidity correction is not required within this range.

Atmospheric pressure correction may also be required according to Gastec's official measurement procedure.

Possible Interferences

Certain coexisting substances may affect or produce color changes during Gastec 91P measurements.

Ammonia: At concentrations of 2 ppm or less, Gastec identifies no interference and no independent color change.

Nitrogen Dioxide: At concentrations of 1 ppm or less, Gastec identifies no interference and no independent color change.

Acetaldehyde: May produce a positive interference and can independently produce a pink color change.

Acetone: At concentrations of 0.3 ppm or less, Gastec identifies no interference with the formaldehyde measurement; however, acetone may produce a pink color around the tube inlet.

Ethanol, Ethyl Acetate, p-Dichlorobenzene and Toluene: Gastec identifies these substances as producing no interference under the manufacturer's specified test conditions.

Coexisting gases and vapors should always be considered when interpreting detector tube results.

Refrigerated Storage Required

Gastec 91P Formaldehyde Detector Tubes must be stored refrigerated.

The manufacturer specifies a 12-month shelf life when stored in the refrigerator. Improper storage conditions may affect detector tube performance and measurement reliability.

Always follow the storage requirements and expiration information printed on the detector tube packaging.

Important

A compatible automatic air sampling pump is required for correct use of the Gastec 91P Formaldehyde Detector Tubes.

For the primary 0.02–0.4 ppm range, sampling is performed at 200 mL/min for 30 minutes, producing a total sample volume of 6,000 mL.

For the extended 0.4–1.44 ppm range, a fresh tube is sampled at 200 mL/min for 10 minutes, producing a total sample volume of 2,000 mL, and the detector tube reading is multiplied by the 3.6 correction factor.

Do not use a standard manual detector tube pump in place of the required automatic sampling method.

Temperature correction must be applied according to Gastec's official 91P instructions.

Always follow Gastec's official instructions for sampling rate, sampling time, sample volume, correction factors, environmental conditions, storage requirements, possible interferences, and interpretation of results.

Compatible Pump: Gastec GSP-501FT Automatic Air Sampling Pump

Choose Instrument Depot for dependable Gastec 91P Formaldehyde Detector Tubes, HCHO detector tubes, formaldehyde air testing, low-level formaldehyde monitoring, indoor air quality testing, Gastec automatic air sampling pumps, Gastec GSP-501FT sampling pumps, industrial hygiene air monitoring, workplace formaldehyde monitoring, gas detector tubes, and industrial gas detection equipment.