Don’t forget about your lab’s moisture traps/filters, especially when it’s summer

One of the common issues which arise in laboratories during the summer is moisture in the gas lines. Although I never quite understood how this would happen when using gas cylinders, it does, especially when a manifold system is used, or if the length of tubing from the gas source to the instrument is longer than several feet/meters.  Common observations when this happens are:

  1. Unstable instrument detectors (especially TCDs, HIDs, ECDs and mass specs).
  2. Less than ideal chromatography (shifting retention times, unusual peak shapes, etc.).
  3. Unusual activity issues in the injection port and/or ghost peaks.


So what is an inexpensive way to minimize these issues, especially in the summer when many locations experience hot and humid conditions? Install an indicating moisture trap/filter on all gas lines.


So how would you know which trap filter would be best for you laboratory? Ask yourself the following questions:

Q1. What is the gas?

Q2. Is the gas line tubing copper or stainless steel?

Q3. What is the maximum gas flow rate the trap/filter may be subjected to?

Q4. What is the maximum gas pressure the trap/filter may be subjected to?


Here are my suggestions to aid in trap/filter selection based upon the questions listed above:

S1. Generally speaking, the traps/filters we sell are for use with laboratory grade (high purity) inert gases.  If you plan to use a Restek trap/filter with a corrosive, flammable or reactive gas, email us first at

S2. Most use traps/filters containing brass end-fittings with copper tubing and stainless steel end-fittings with stainless steel tubing.  For additional information on the topic, I suggest you review I need a fitting, but which one?

S3. Published flow rates can vary among manufacturers, so make sure you are aware of exactly what a published value represents.  For example, is the published flow rate the maximum flow rate the trap/filter can handle, or is it the maximum flow rate in which the trap/filter can effectively clean (scrub) the gas?  In the context of this post, what is the maximum gas flow rate through the trap/filter that can effectively remove much of the moisture?

S4. For obvious safety reasons, make sure the published maximum trap/filter pressure is not exceeded.


Several of the popular indicating moisture filters are shown below.


Indicating Moisture Trap



Restek Super Clean Ultra-High Capacity Moisture Filter



Don’t forget the baseplate.

Of course we also sell a wide variety of other filters including non-indicating moisture filters, and others for the removal of oxygen and/or hydrocarbons.   To view all of your options, click on the link below.


Or for removal of a specific contaminant(s), the links below may be quicker to navigate:

Moisture Removal

Oxygen Removal

Hydrocarbon Removal

Multiple Gas Removal


You may also find these links (below) informative. If you have any questions, you may email me directly or technical service at .


SDS’s for 22010, 22011, 22014 and 22015 (Indicating Oxygen & Moisture traps/filters)

Several things you may not know about our Super-Clean® Gas Filters

Contents inside your baseplate trap

Indicating Oxygen and Moisture Traps-“Hey, it looks like my trap arrived partially spent”

Did I just break my hydrocarbon trap (22012 and/or 22013)?

SDS (MSDS) for VICI® Mat/Sen® Gas-Specific Purifier Modules

6 Responses to “Don’t forget about your lab’s moisture traps/filters, especially when it’s summer”

  1. Dear Alan,

    Very interesting topic to bring up! During my >25 years with gas chromatography, I have experienced quite a lot of gas cleaning issues related to summer periods. A significant number of those issues were related to vacation periods! People who are responsible to keep gas delivering systems up and running, unfortunately also need vacation. -:) Even if substitutes are well educated and have nice SOP’s and operating guides to follow, it will quite often leed to failures, due to lack of experience with the gas delivering systems. We have observed those kind of issues both in-house in our labs as well as at gas delivering companys! Mu-ha-haaa! The latter one is very difficult to investigate, I can ensure you ….. -:)

    Kind regards –
    Lars Kürstein

  2. Alan Sensue says:

    Hi Lars: Thank you for reading my post and your reply. I, like you, remember instances where contaminated gas lines caused instrument downtime. One instance in particular I remember well. It was summer and we decided to resurrect an instrument which had been sitting idle for some time. The gases were plumbed through a manifold set-up. Before connecting the carrier gas tubing to the instrument, I thought it would be prudent to “blow-out” or “flush” the gas line, and good thing I did because a stream of water shot out of the fitting. After that I became a lot more diligent about having a moisture trap/filter installed on every line. Regards, Alan

  3. Amit Gujar says:

    Hello Alan,
    A very timely article…I was thinking about traps (moisture, oxygen, HC) a few weeks ago. Just to confirm my calculations- A UHP grade Helium is 99.999% pure. That would be 0.001% of contaminants…that is 10 ppm of contaminants (based off 1% is 10000 ppm). So when you have traps like this- which say it reduces oxygen to 15 ppb which is 666 times reduction (lets assume 0.001% contaminant is O2)…
    Is this calculation correct? I have heard many times people say-“…Oh its UHP grade or Research grade (6 nines); you probably dont need a filter…”…I would say that if this calculation is correct then a filter is definitely needed even with Research grade gas (again it depends on the final application).

  4. Alan Sensue says:

    Hello Amit: Thank you for reading my post and your question. Here is my understanding on how traps/filters work; they remove a certain portion of the contaminant(s) if the flow rate is kept below a certain value, which is typically published by the manufacturer. Years ago I had been taught that the portion of contaminant(s) a filter/trap removes is an order of magnitude from the incoming gas. For example, if the incoming gas has 10ppm of moisture, the outgoing gas will have approximately 1ppm moisture in it. I am fully aware that this is an over-simplification of what really happens, but I find it easy to remember and to explain to customers, much like I was taught years ago. I hope this helps. Regards, Alan

  5. Dear Alan,

    There must be a range of contaminants which can not be removed from clean gases by use of routine/standard moisture-, oxygen- and hydrocarbon filters. Methane, for example? Others?

    With kind regards –
    Lars, Copenhagen

  6. Alan Sensue says:

    Hi Lars: I am certain that there are contaminates which cannot be removed from each type of filter/trap, but sometimes just as important, there are gases which are not contaminates which may also be inadvertently removed from a gas/sample stream by one of these filters/traps. Unfortunately, unless published, the only way to know would be through extensive experimentation. In summary, I do not have a conclusive answer to your question. What I can tell you is that I am not aware of any trap/filter which can remove methane from a gas stream, including a hydrocarbon trap/filter. I can also state that many moisture traps/filters contain molecular sieve 13X which will also remove a portion of CO2, H2S, SO2, HCl vapors, etc.. (if present) from a gas stream. Sorry, I wish I could have been of more help. Regards, Alan

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