Odour Sampling - St. Croix Sensory, Inc.

FAQs

Q: How much air do I put in a sample bag?
It is best to fill a sample bag 1/2 to 2/3 full. This gives the bag some space to expand if shipping the samples by air courier. If you fill the bag completely full on the ground, a seam can split as the bag expands under low pressure in flight.

Q: How many turns do I open the valve?
The valve is designed for one-full turn of the valve to open. Grab the main valve body and twist it counter-clockwise 1 to 1-1/2 revolution. If you keep turning the valve multiple turns, the top of the valve will come off, which is convenient for emptying a bag. The top is easy to put right back on. NOTE: turning the brown top of the valve will only open up access to the septum.

Q: What sample volume is needed for odour analysis?
A 10-L sample bag should be used for collecting odour samples. St. Croix Sensory needs about 5-L of air sample for olfactometry analysis for threshold and direct evaluation for odour intensity and characterization.

Q: What is the sample holding time of sample bags?
Industry standard is a 30-hr holding time, which provides time to collect samples and send them over-night to a laboratory for next day analysis.

Q: Where do I get odour sampling equipment?
St. Croix Sensory is a manufacturer and supplier of odour sampling equipment. Equipment is available for both rental and purchase. Please contact us for specific information about the equipment you may need.

Q: How should I ship sample bags for analysis?
St. Croix Sensory can supply you with partitioned shipping boxes for your project at no extra cost. Sample bags should be placed in a shipping box with the valve end down. Bags should never be stacked in a shipping container as the weight of multiple bags under pressure during air transport could split the seam on a bag at the bottom of the stack.

All odour samples should be analyzed within an industry standard of 30-hours. This requires samples to be shipped to St. Croix Sensory via priority overnight shipping (e.g. UPS or FedEx). In some cases, early AM delivery may be necessary from some locations and depending on the time samples were collected.

St. Croix Sensory provides shipping boxes at no charge (charge for shipping). These boxes can be sent directly to your sampling site for your convenience. Please contact us for specific information about shipping.

Q: What is ASTM E679?
ASTM E679 is an ASTM International standard method for determination of odour thresholds by a triangular forced-choice testing method. This standard was first published in 1979 as E679-79, when it replaced the static threshold “Syringe Method”, ASTM D1391. In 1991, minor revisions were made and the standard was renumbered E679-91. In 2004, additional examples were added to the standard and was renumbered E679-04. The newest revision, published as E679-19, included only minor edits for clarity.

Q: What is EN13725?
EN13725 is a Committee European Normalisation (CEN) standard method for “Determination of odour threshold by dynamic olfactometry.” EN13725 exceeds the requirements of ASTM E679 with additional QA/QC and assessor selection requirements. This was first published in 2003 and a first revisions has been published in 2022 as EN13725:2022.

Q: What type of olfactometer does St. Croix Sensory use?
At St. Croix Sensory, we utilize the AC’SCENT Olfactometer. We developed this olfactometer in the 1990’s to meet the newest requirements of ASTM E679 and EN13725. We run this olfactometer operating in Triangular Forced-Choice mode with a 20-LPM presentation rate. The AC’SCENT can also be operated in Binary Forced-Choice, Yes/No, or Direct Presentation testing modes. The AC’SCENT can also be operated at flow rates of 3-LPM to 20-LPM.

Q: What are odour units?
Odour units are a pseudo-dimension applied to odour threshold testing results from testing with an olfactometer. The olfactometer threshold result is a dimensionless dilution ratio. Frequently, the units of “odours units” (O.U.) or “odour units per cubic meter” (O.U./m3) are applied to the result.
This dimensionless value refers to the average dilution ratio at the threshold or the number of dilutions needed to bring the odour to this threshold.

Q: What is Odour Intensity?
Odour intensity is determined following ASTM International E544, “Standard Practice for Referencing Suprathreshold Odor Intensity.” It is a measure of the perceived strength of the odour.

Q: How long does it take to receive my results?
For environmental odour evaluations, St. Croix Sensory provides a detailed electronic report within 5-business days after evaluation. In most cases, reports are received 2-3 days after evaluation. Fast guarantee report turn-around can be provided at an additional charge.

Q: Does the VAC’SCENT comply with EPA sampling methods?
Yes, EPA Method 18 – Measurement of Gaseous Organic Compound Emissions by Gas Chromatography and Method 0040 – Sampling of Principal Organic Hazardous Constituents from Combustion Sources Using Tedlar Bags.

Q: When I sample, how do I minimize contamination between samples?
Change or purge the Teflon sampling tubing after each sample collection.

Q: Do I need a pump with the VAC’SCENT?
No, the VAC’SCENT has a pump inside. However, if you need to collect a sample over a long period of time (10-minutes to 60-minutes) we recommend you use a variable speed personal sampling pump externally to create the vacuum inside the VAC’SCENT.

Q: What sample tubing should I use?
Teflon tubing should be used for collecting odour samples. St. Croix Sensory can provide you 1/4″ Teflon tubing.

Q: What are the ports on the chamber?
There are four ports on the front of the chamber. Ports A & B (front left) are the integral pump outlet and inlet. Port C is a valved port for depressurizing the case. Port D is the sample inlet port. Connecting Port B to Port C will evacuate the air in the case. The sample will then flow into Port D, and then the sample bag, to balance the pressure.

Q: What size sample bags will fit in the VAC’SCENT?
The VAC’SCENT can be used to fill two 10-L sample bags at one time. This allows for collection of true duplicates. A 25-L bag can be used if the dimensions of the bag are appropriate. Please contact us if you have specific needs. The VAC’SCENT can be built with cases of varying sizes.

Q: Does the AC’SCENT Flux Hood comply with EPA sampling methods?
Yes, see EPA document PB86-223161, “Measurement of Gaseous Emission Rates from Land Surfaces Using an Emission Isolation Flux Chamber.”

Q: When I use the Flux Hood what flux gas/air do I use?
The protocol for your project may dictate zero-air or high-purity nitrogen (HPN) with or without a helium (He) component.

Q: What is a typical sweep gas (air) rate?
25-liters per minute per square meter is a typical sweep gas rate, which is 3.5-LPM for the 0.13-m2 under the AC’SCENT Flux Hood.

Q: What is the typical sample collection rate?
The Sample collection rate depends on your project protocol; a typical sample collection rate is 1 to 2 LPM.

Q: Can’t I just use any tubing for odour collection?
The inert properties of Teflon tubing make it the standard for odour collection. It is still suggested to replace tubing for each sample collection.

Top Notes from the Lab

Featured – Top Notes from the Lab