Is there a procedure on how to clean the Model 106-L?

Technical Note No. 042

Cleaning Procedure for Model 106-L Ozone Monitor 

Date: 8 June 2016

Author: Chris Ennis

Summary:
It is recommended that Ozone Monitors be returned to 2B Tech at least once annually for 
calibration. This includes cleaning of the entire flow path and installation of a new internal 
ozone measurement scrubber (Figure 5.1 of the manual for the Model 106-L Ozone 
Monitor). If the flow path becomes contaminated, as evidenced by large positive or 
negative offset (Z) and/or low slope (S) calibration parameters, it may be necessary to 
clean the flow path and replace the ozone measurement scrubber. This can be done by 
the user if desired. The procedure involves the following steps:

1. Remove the top cover.
2. Bypass the ozone measurement scrubber.
3. Bypass the DewLine™ (Nafion tube).
4. Connect a drain tube at the exit of the detection cell.
5. Squirt methanol through the flow path while the instrument is running.
6. Blow dry with clean compressed air or nitrogen while the instrument is running.
7. Check the DewLine™ for contamination.
8. Replace the ozone measurement scrubber.
9. Reconnect plumbing.

Tools needed:
-Philips head screwdriver
-Teflon®-lined Tygon® or other clean, inert tubing such as PTFE, PFA or PVDF
-Methanol (methyl alcohol)
-Squirt bottle
-New ozone measurement scrubber

Please refer to Figure 5.1 of the Ozone Monitor Model 106-L manual as you go through 
this cleaning procedure.

Procedure:
1. Remove 6 screws from top cover. Remove cover (blue), from base (white).

2. Bypass the ozone measurement scrubber and disc particle filter by disconnecting both 
ends of the scrubber and replacing with a short piece of clean, inert tubing such as 
Teflon-lined Tygon®, PTFE, PFA or PVDF. Do not use Tygon!

3. Remove the DewLine™ at both ends and replace it with clean, inert bypass tubing 
such as Teflon-lined Tygon®, PTFE, PFA or PVDF. Do not use Tygon! 

Note that the DewLine™ consists of two sections of Nafion® tubing connected in 
parallel. 

4. Disconnect the tubing from the outlet of the detection cell and replace with a drain 
tube. The drain tube can be any kind of tubing; silicone tubing is shown here. 

Use a squirt bottle to force methanol through the flow path while the instrument is 
running. You should pass at least 50 cc of methanol through the instrument. The 
purpose of having the instrument running is to clean both sides of the 3-way solenoid 
valve. This valve switches states every 2 seconds. 

6. Dry the flow path with clean, compressed air or nitrogen. Be careful during this 
step and use low pressure to begin with as large quantities of methanol will 
spew out initially. IMPORTANT: It is necessary that the flow path be completely 
dry before reconnecting the scrubber.

7. If the DewLine™ has become contaminated (as noted by discoloration), it should be 
replaced, or returned to 2B Technologies for cleaning.

8. It is recommended that you replace the ozone measurement scrubber (the one you 
bypassed) during this step. If the flow path was dirty, then the scrubber will be dirty 
as well. A contaminated ozone measurement scrubber will typically cause a large 
offset in the measurement and may re-contaminate the flow path. The ozone exhaust 
scrubber on the opposite side of the instrument that protects the air pump may be 
changed at this time as well, although that ozone scrubber has no effect on the ozone 
measurement.

9. Reconnect the plumbing and replace the instrument covers. The assembled Model 
106-L instrument is shown below as a guide. (Reproduction of photo from Figure 5.1 
of the Model 106-L manual.) 

10.We recommend that you run the instrument at least an hour or two after cleaning, to 
ensure that it is thoroughly dry before you resume measurements. Place an external 
ozone scrubber on the Model 106-L air inlet for this step.

Additional Cleaning: 
When calibrated, the Ozone Monitor should have an offset (Z) in the range ±10 ppb and 
preferably ±5 ppb. The slope calibration parameter (S) should be in the range 0.90-1.10 and preferably 0.94-1.06. Offsets and slopes outside this range are most often due to a contaminated flow path. Sometimes it requires more than one cleaning to correct a highly contaminated instrument. If methanol alone is not adequate, it is helpful to do a first cleaning with hexane and a second cleaning with methanol. All of the cautions concerning the use of methanol apply to hexane as well. If cleaning of the flow path in combination with replacing the ozone measurement scrubber does not correct the problem, please return the instrument to 2B Technologies. We will provide you with an estimate of any required repairs before doing the work. 

If you have an ozone source, it is helpful to 1) clean the instrument with methanol, 2) 
expose the instrument to high ozone levels (ppm and above) for several minutes to hours, 
and 3) clean the instrument again with methanol. The ozone will oxidize contaminants to 
form polar oxygen-containing compounds that are more soluble in methanol.

Note: You can check the zero of the instrument by running it with an external ozone 
scrubber attached. Keep in mind that the external ozone scrubber must be clean; 
otherwise, it will desorb UV-absorbing compounds and cause an apparent offset.