[3dem] Cryo-prep lab humidity and temp control

Fri Feb 13 02:55:55 PST 2026

Hello,

All of Ruben's suggestions are good! (Commenting only as a user of a different facility.)

Keeping humidity below 30% is very helpful. Here we have the vitrification lab at the end of a larger lab space, not under humidity control, and we can really tell that there's a better season to prepare grids. Right now, with outside temperatures below freezing, it is great: the air is very dry. I vitrified and clipped earlier this week, the hygrometer reported ~15% RH: I could take my time and got almost no frost build-up. This can make a big difference for beginners learning to vitrify and clip, it really takes one source of stress away.

I simply wanted to add that, if you choose humidity control to keep the air very dry in this room, get an anti-static gun: https://urldefense.com/v3/__https://www.fishersci.com/shop/products/anti-static-gun-2/nc9663078__;!!Mih3wA!HletJdADV_QC0MLjOGAENliG0bDDs_XGMcjHAw3Xf8YvhPeN14pqBIyZd2fu8A_IwLnifzuO0oB8ab6WX1wWdq2fxqahPBLL$ 

If applied carefully to all tools, it can minimize the problem of grids sticking to tweezers or lids of the grid boxes (which in my experience is made worse by dry conditions), which is a massive pain even when you are used to handling grids. The only thing you don't want to zap with this tool is freshly glow discharged grids (it would cancel it), but once vitrified I have zapped grids and tools and it's fine.

Your users will thank you!

Cheers,

Guillaume

________________________________
From: 3dem <3dem-bounces at ncmir.ucsd.edu> on behalf of Ruben Diaz Avalos via 3dem <3dem at ncmir.ucsd.edu>
Sent: Friday, February 13, 2026 6:16:07 AM
To: Errin Johnson
Cc: 3dem at ncmir.ucsd.edu
Subject: Re: [3dem] Cryo-prep lab humidity and temp control

Hi Errin,

These are largely personal preferences, and you will likely get different answers from different people. In my view, the sample preparation room should be large enough to comfortably accommodate a Vitrobot (or two, if available), a couple of single-sided plungers, a glow discharger, a large dewar or two for specimen storage, an ethane tank, and a separate desk for grid clipping. Realistically, this means a room of at least ~4 m × 5 m.

Relative humidity should ideally be as low as possible. While 0% is not realistically achievable, anything below ~30% is acceptable, and aiming for ~20% is a good practical target. Low humidity significantly reduces frost contamination during grid handling.

The room should not be cold, which can happen if the reheat coils are not functioning properly. We try to maintain ours at ~21 °C, although it fluctuates between ~18–24 °C, which is generally tolerable for most people and compatible with stable sample preparation.

Ventilation is critical due to the large volumes of nitrogen handled during freezing and storage. The room should have a high air refresh rate and be equipped with low-oxygen alarms for safety.

Humidity control can often be achieved with one or two high-capacity dehumidifiers that can be activated prior to cryo-grid handling. In some facilities, it is also necessary to have a safe way to vent or dispose of ethane as it warms after freezing sessions — for example, access to a nearby chemical fume hood.

With best regards,

Ruben.

**********************************************
Ruben Diaz Avalos, Ph.D.,
Director of Electron Microscopy,
La Jolla Institute for Immunology,
9420 Athena Circle Dr.,
La Jolla, CA 92037
(858)752-6960
**********************************************

On Thu, Feb 12, 2026 at 7:47 PM Errin Johnson via 3dem <3dem at ncmir.ucsd.edu<mailto:3dem at ncmir.ucsd.edu>> wrote:
Hi all,

We are in the design phase for a new cryo-EM Facility and are currently having discussions with the architects about the temperature and humidity specifications for the cryo-sample prep lab. It would be really useful to benchmark our design against other facilities that have been purpose-built for cryo-EM.

Specifically, it would be great to have info on:

  *   Cryo-sample prep lab dimensions
  *   Set points for both temperature and humidity, plus the tolerance range for each, in the design, what is achieved in practise and how well this is working for cryo-EM grid prep
  *   Whether a push button (or similar) system is used as a de-humidification boost when users are preparing grids, with the humidity conditions relaxing outside these times, and how well this is working in practise

If anyone has gone through the throes of cryo-EM facility design in the last several years and could provide answers to these questions I would very much like to hear from you!

Best wishes,

Errin

Dr Errin Johnson (She/Her)| Bio EM Section Manager
Sydney Microscopy & Microanalysis | Core Research Facilities

THE UNIVERSITY OF SYDNEY
Rm 116A, Madsen Building F09 | The University of Sydney | NSW | 2006 | Australia
T +61 2 93519826
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--
**********************************************
Ruben Diaz Avalos,
La Jolla Institute for Immunology,
9420 Athena Circle Dr.,
La Jolla, CA 92037
(858)752-6960
**********************************************

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