Ah fresh air! It's the stuff of life itself and we all need it full-time. Unfortunately, it's often in short supply in the darkroom. And fresh air is more than a matter of basic comfort. For those of us who spend a lot of time in close proximity to various photo chemicals, it can be a matter of health as well. Your lungs have no veto power; if there are irritating or dangerous chemicals in the air, you either breathe them or get some ventilation going. (Leaving the room or holding your breath are not good options, since they make it hard to get work done)


In commercial labs, you'll find ventila-tion fans doing several kinds of duty, depending on the needs of the workers. These systems can be divided into "pos-itive pressure" (blowing air in) and "negative pressure" (blowing air out) types. Let's take a look at the various situations where ventilation is needed, the particular problems of each situa-tion, and how proper ventilation solves the problem.

Many labs have several small print-ing rooms, containing no water or chemicals (a home analog would be a closet which has been converted into a darkroom). Put a darkroom technician and a 250-watt enlarger in one of these rooms, and in no time at all the heat goes up and the air quality goes down. This is the classic instance requiring a positive pressure blower, which forces fresh air into the room.

That's fine for the dry-side, but what about chemical-filled areas? Anyone who's ever printed black-and-white knows that acidic fumes rise off the stop and fixer trays. The best way to deal with them is to place a medium-sized negative pressure ex-haust fan just above and behind the stop and fix portion of the tray line. In this way, the fumes are pulled out of the room as they rise. This type of ventila-tion is also used by commercial labs over large machine processors.

Chemical mixing is probably the most hazardous duty in the lab. As various dry and liquid chemicals are poured into the mixing water, dust and fumes float up in relatively high concen-trations. So the mixing area requires a powerful exhaust fan to remove chemi-cals from the air before they are in-haled.


Just how dangerous are darkroom chemicals? Well, stop bath and fixer fumes are more irritating than danger-ous; they combine with moisture in our eyes and respiratory tracts to form acids which burn those delicate tissues. You won't die from this, but it does cause a constant stress, which some people don't seem to notice but which is there all the same. Complex developing agents, on the other hand, can cause severe allergic reactions if exposure is chronic. Some of the color chemicals are very toxic, and direct contact is to be strictly avoided.

Commercial labs are subject to local codes and OSHA (Occupational Safety and Health Administration) guidelines for worker safety and comfort. This is on the right track, but all too often the standards are not met. As in the case of the home photo lab, there's only one ultimate watchdog: you, the person who works there. If the chemicals bother you, get something done about it fast. Even if you don't notice any dra-matic problem, you owe it to yourself to install some form of ventilation if you do darkroom work on a regular basis.


Before you install a ventilating system, you'll want to carefully consider the specifics of your particular darkroom situation. Having ventilation that doesn't work right can be worse than not having it at all. Here are some points you'll want to consider.

The ventilation system must, in most cases, be lightproof. Blowers and fans made for darkroom use are likely to meet this requirement, but if you're going to install a simple bathroom fan or kitchen-type blower, you'll have to seal it carefully and use enough elbows in the ducting, through which the air will travel, to baffle the light.

Airflow is an important considera-tion. In a positive pressure system, where does the stale air go? If the room is not a tight one, it will escape through cracks and around the door. But if the room is tight, you'll probably have to place a light-tight grille or louver in the door or on a wall. Likewise, with a negative pressure system, the air must come from somewhere; installing a grille or louver makes it easier for the fan to pull fume-laden air from the darkroom.


Positioning the fan is important too; the direction of airflow must be taken into account. I once worked in a university darkroom in which the exhaust fan was on the ceiling, behind me as I stood at the processing trays. Fumes were pulled directly into my face as I worked. This sort of poor design can easily be avoided if you take a little time and give the layout some thought. You'll also have to consider just where and how the ducting will come into or out of the room. High on a wall is the best place for a positive pressure fan; in most cases you'll want to pull air in from the next room rather than from outdoors. With negative pressure sys-tems, though, the fume-laden air should be blown directly outside the building. A window can usually be modified to let ducting through, or it may be best to make a hole right through the exterior wall.


Dust is a problem in any darkroom, and if your ventilation fan is pushing or pull-ing dusty air into the lab, the problem increases. Fortunately, the solution is simple: just place a furnace filter over the fan (positive pressure) or over the louver (negative pressure). In this way, any air that enters the room is prefil-tered.

Noise is another concern when you decide to install a fan. If it's a fan which will run all day, such as an exhaust unit over the stop and fix trays, you'll want it to be quiet. In a mixing area, though, power is the main requirement; since the fan is only operating occasionally, noise becomes a secondary considera-tion. If you're buying a fan, plug it in and assess the noise level before pay-ing for it.

Once you've planned the system carefully, you have the option of install-ing the system yourself or having a professional contractor do the work. If you don't know a hole saw from a pop-rivet, you'd be best off going to a pro. But if you're competent with tools, it's really a simple procedure. After buying the necessary materials, posi-tion your fan, keeping in mind the con-siderations discussed above. Next, run the ducting (usually stovepipe) from the fan to the window or through the wall, whichever you decide will be best for your particular setup. Remember that your ducting must be light-tight and weather-proof. Duct tape (available at building supply stores) will hold it together, though you may want to use screws too. Heavy black tape is good for sealing the duct into the hole. Now wire the fan into an on-off switch. Install the louver, usually in the door, and you're set to try it out!


One other device that can protect you from airborne chemicals is the gas mask, or respirator. Some workers wear a mask anytime they mix chemi-cals, even if there's a good ventilator. For the home worker who doesn't really need or can't afford a whole system just for occasional mixing, this is a sensible alternative. Be sure to use the correct type of filter; any mask will work for chemical dust, but for fumes you need an "organic vapor" cartridge. You can also do occasional mixing outdoors; this is especially a good idea when mix-ing fixer, since fixer dust will damage any photosensitive emulsion it contacts.

All in all, ventilation is not only essen-tial, it's too simple and easy to neglect. Spend some time planning, then spend a few dollars and a few hours on an appropriate system. When health and comfort are concerned, all time and money are well spent.

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