Fwd: Darkroom Exhaust Fan Question

[Rebecca]

Rebecca

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Begin forwarded message:

From: Norman Riley <nerph...@yahoo.com>
Date: December 4, 2013 at 11:34:34 PM CST
To: "rebec...@gmail.com" <rebec...@gmail.com>
Subject: Darkroom Exhaust Fan Question
Reply-To: Norman Riley <nerph...@yahoo.com>

Hi Rebecca. 

 

You recently contacted me to ask about the necessity of having an exhaust fan in a commercial darkroom.  In answering this question, I assume the darkroom in question is a community space in which only standard and general purpose chemicals will be used for black and white and possibly color processing.  I answer your question from the perspective of one who has operated a darkroom for 35 years, who worked for the California Environmental Protection Agency (Department of Toxic Substances Control) for over 25 years, and who graduated from the University of California at Davis with a degree in toxicology (i.e., I am trained in the detection, occurrence, properties, effects, and regulation of poisons).  Based on my education and experience as outlined above, it is my considered opinion that an exhaust system in a general-purpose darkroom is superfluous and unnecessary.  In my view, the money that would be spent on an exhaust system in such a facility would be far better utilized on things such as temperature control valves, water filtration systems, GFCI outlets, enlarging easels, timers, trays, grain magnifiers, and print washers.  If air circulation is considered a problem for reasons of bodily comfort, then a combination of "light-tight" or "light-proof" louvers, e.g., http://www.bhphotovideo.com/bnh/controller/home?O=&sku=43104&is=REG&Q=&A=details and portable fans, or a simple bathroom or kitchen-type exhaust fan would be sufficient.  [Please note that I point to the Doran louver only for purposes of illustration.  No endorsement of that product, manufacturers, or supplier is expressed or implied.]  An elaborate and costly exhaust system may be helpful in circulating air to control humidity or minimize airborne dust by means of positive pressure, but it is not needed to address toxicological threats because no such threats are presented to most people by the developing, stop, and fixing solutions used in normal darkroom work. (It is important to note that people suffering from bronchitis, sinusitis, or asthma, for example, may be susceptible to problems in the darkroom that do not affect healthy people).  That is not to say that photochemicals themselves present no dangers at all.  Some of them certainly are dangerous if and when mishandled (e.g., if powders are inhaled or ingested) but short term exposures associated with safe, sensible, and normal darkroom practice pose no significant threats to the majority of darkroom workers, notwithstanding the hysterical and uninformed warnings that one occasionally finds in the vast pedestrian deposit that we call "the internet." 

 

Developers used in traditional black and white darkroom work are typically combinations of  metol (aka "elon") and hydroquinone along with an accelerator (typically sodium carbonate), a preservative (typically sodium sulfite), and a restrainer (normally potassium bromide).  None of these ingredients when mixed in stock or working solutions are volatile and therefore none pose an inhalation hazard once in solution.  As you may know, there are some persons who develop a contact dermatitis (i.e., a skin allergy) to metol, but this is not a problem that can be mitigated by the installation of an exhaust system.  (It can be mitigated only by using gloves or switching to an alternative developer such as phenidone that does not cause an allergic reaction.)  The active ingredient in the customary stop bath is acetic acid.  While this material has an odor, it is far from dangerous.  Acetic acid is essentially "vinegar." As an aside, I would recommend that you use 1 part distilled white vinegar to 3 or 4 parts of water to make a suitable and economical stop bath vs. spending money on more expensive preparations available from various suppliers.  For film, you do not need to use an acid stop at all: plain water is perfectly adequate and will not cause pinholes as may occur when going from an alkaline developer to an acidic stop. The odor emanating from the common fixing bath is sulfur (evolving from sodium thiosulfate, the active ingredient in the fixing bath).  While some may find this odor objectionable, many do not and the concentration of sulfur in any case is not high enough to exert a toxic effect in a healthy person.  The odor emanating from a selenium bath is ammonia, a reaction product, which is not a problem when the toner is used as directed, i.e., at about a 1:20 dilution, even when standing directly over the bath for a period of several minutes.  It is very important; however, to always wear gloves when using selenium toner.  Likewise, it is extremely important to assure that all spent solutions are handled appropriately.  All MQ developers oxidize rapidly and can be discharged to POTWs.  Spent fixing solutions (specifically those containing 5 parts per million or more of silver) should be treated to remove silver before discharge to sewer systems because silver is a persistent and bioaccumulative toxin.   Likewise, selenium solutions (above 1 ppm) should also be treated prior to disposal (or managed by a qualified waste disposal company), and the same applies to spent chromium solutions containing 5 ppm or more of hexavalent chromium (as may occur if chromium intensification is allowed to be conducted in the darkroom.  Check with your local health (city or county) department to be sure that any special quidelines adopted by them for photo darkrooms are followed.  Color chemistry is more exotic and in some cases more toxic than black and white chemistry (e.g., some stabilizers contain formaldehyde), but still not dangerous when recommended procedures are followed. Here too, I would advise that you check with your local health department to assure that all necessary requirements are understood and adhered to for the management of all secondary materials, whether resulting from color or black and white work. 

 

I hope the foregoing answers are helpful to you and your colleagues. If I can be of any further help to you, please let me know.  Congratulations on the siting of your community darkroom.

 

NER