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

[Ruben Diaz Avalos]

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>
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
>
> *E* *errin.johnson at sydney.edu.au  <errin.johnson at sydney.edu.au>*| *W* *sydney-microscopy-and-microanalysis/our-staff.html
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>
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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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