This page outlines our 2012 Olfactometer. It is easier to construct compared to the 2003 Olfactometer but responds less rapidly. Included in this page are directions for construction, a parts list, and cleaning and maintenance methods.
Other Olfactometers may have more precise control over odor release; however, this olfactometer is accurate enough for use in some EEG and most fMRI studies.
Our design is originally derived from Lorig,T.S., Elmes, D.G., Zald, D.H. & Pardo, J.V. (1999). A computer-controlled olfactometer for fMRI and electrophysiological studies of olfaction. Behavior Research Methods, Instruments & Computers, 31,370-375.
This model continues to refine the design and ease of use of the Olfactometer.
The design is relatively simple to build and operate. The idea of the olfactometer relies on one constant flow line being operated by a computer controller. To administer odors, air flow is switched to flow through syringes with the odors inside. The constant flow line is stopped during odor delivery and switched back on upon termination of odor delivery. This air is unodorized and results in a net change of zero for air flow throughout the experiment.
The air pump used is commercially available through a nebulizer supply company (Respironics although many others will work as well). The air flow may be filtered through charcoal filters to rid the air of bacteria and odors naturally occurring within the air. NOTE: IF A CHARCOAL FILTER IS USED, A PARTICULATE FILTER MUST BE USED TO REMOVE CHARCOAL DUST. Otherwise you run the risk of exposing your subjects to this dust. We pull our air from a room without odor contamination and do not use a charcoal filter. We suggest you do the same.
Following particulate filtration, the flow of air is divided through two flowmeters (rotometers). Valve A provides a low and constant volume of air (Normally On- NO). Valve Bn is connected to the odor delivery line, where odors pass through odor-containing syringes and to the participant (B1-B4). To deliver an odor to a participant, the computer activates Valve A (interrupting air flow in that line) and Valve Bn (allowing line Bn air to flow). Air flow then passes through the syringe connected to line Bn, proceeding through the manifold and then to the participant. After administration of odor, the computer switches Valves A and Bn to the off position, deactivating line Bn and opening line A. A pressure transducer connected to the nasal canula can be used to detect breathing cycle and regulates aidminstration of the odor via the computer control.
Line A acts as a "buffer" between air flow changes of line Bn, which last ~20ms.
Pictured below is the valve assembly, refined from 2003 with simplicity in mind. 2 syringes are pictured for a 2-odor study; the manifold allows for a flexible delivery of 1-4 separate odors as desired. The constant air flow line is marked with a black piece of tape. The manifold is located at the left of the picture, with a separate line for constant air flow. All lines converge on one delivery line that delivers odor to the participant. Odors do not stick within the tubing because of the tubing used (Bev-a-line V). This tubing is lined with PTFA via a sintering process. The tubing provides both the flexibility of poly propylene with the non-stick properties of teflon.
The syringes used are made for tissue perfusion under pressure and fasten via luer locks. These fasteners use check valves, which have a silicone membrane that can react with some odorants such as amyl acetate.
Odor is delivered to the participant through disposable dual lumen nasal cannulas, which are commercially available. Pictured below, the canula is connected to the air flow via a needle with luer hub for connection. The cannula is divided into two different lines, one for air pressure (right) and one for odor delivery (left). Odor delivery is not administered through the tubing of the cannula, but through the needle line connected to the nose piece thus bypassing the tubing.
Figure 3. (Pictured in black and white to show contrast)
Electronics and software remain the same from the previous olfactometer, and can be found here.
Because odor should not pass the check valves, the four odor supplies do not have to be changed or cleaned after a study. Syringes will need to be cleaned or replaced after each study.Additionally, particularly sticky molecules such as vanilin or musks may adhere to the PTFA common line to the nose piece and will need to be replaced.
Note: Do not used any natural odor producing products that could decay in the odor vessels. We suggest using only FDA approved flavoring agents available from chemical supply houses.
The parts list below is only for the additions from the previous version as seen in Figure 2 & 3. Electronics and air supply are covered in the 2003 parts list. Note these are the suppliers we have used and others may also have the appropriate parts.
8 cylinder to pressurize/oxyenate solutions (PC-50)
10ft Bev-A-Line V (1/16 ID) (this presumes you already have tubing to the syringes)
1 PTFE 6-way manifold EW-06473-04
1pkg Luer check valves EW-30505-91
Small Parts www.smallparts.com
assorted luer fittings
male luer to hose barb
female luer to male elbow
1/4-28 to female luer
1/4-28 to 1/16 hose barb
1 pkg S/S Needles w/ Luer Hub 14Gx1 NE-142PL-C
Tinal's Home Care
Hudson dual lumen cannual (5 or 7 ft)