Recommended ventilation system?

I am designing my rental darkroom and I need a ventilator fan system. With odor free chemistry these days, and the fact that the space is a kind of large for a darkroom, I am not trying to be a perfectionist here. However, the room I'm setting up in has a drop ceiling that goes to a 2nd floor room (with no floor, so really think of it has just a high ceiling, weird I know). There is a spot there where the air can exit.

I'd like something relatively easy to install and not extremely expensive. Any ideas?

Look at bathroom exhaust fans - and pay attention to the capacity and noise ratings.

I went with a switched bathroom exhaust fan along with a Honeywell HEPA air purifier and an anti-static Ionizing air blower. The three together makes for good air ventilation and dust control combo.

Regards,
Mike

There are a couple things I don't like about bathroom fans. One is you pay for features that might not matter much - like quiet operation, integrated lighting and appearance of grill. But the more serious problem is they have a single inlets and use 3", in some cases 4" exhaust ducting that works okay if you are ventilating a bathroom but is not really adaptable if you decide to add drops later.

You might be better served with an inline 6" fan located where noise is not an issue and closer to your exhaust port, then branching off to smaller diameter ducting to your inlets here and there in your darkroom. That would give you the ability to use multiple inlets and change inlet positioning in the future as you reconfigure your work spaces or as you dial in efficient air movement. Everything you need for such a system is available off the shelf at Lowe's, Home Depot or from an HVAC supply house.

A system like I describe is probably about the same price as a single 100CFM bathroom fan but requires more installation skill. Still pretty easy if you have some basic electrical/metal working skills or are willing to learn as you go - it's not complicated but you might benefit from the advice of local tradesfolks.

It's helpful to have a working knowledge of areas of circles when designing exhaust systems. A quick refresher "radius" "diameter" "pi" and how to use them to determine the area or a circle is important. If you are comfortable with those relationships and understand the term "cubic feet per minute" (CFM) you are well on your way to designing an effective and versatile ventilation system.

Oh, one other thing, don't forget "make up air". You need at least as much fresh air INTO a room as you intend to exhaust out of it.

"Odor free" does not mean healthy. There is no substitute for proper ventilation. First of all, effective ventilation is dependent upon several things. First, you must have the same amount of clean air coming in as you exhaust out, obviously from some kind of light-tight inlet. Second, friction in the air exhaust ducting is just like having too small a garden hose, or a kinked one. That too has to be light-tight. Third, fan rating needs to be at least double the theoretical value due to both duct friction, and even more, pushing against hydrostatic pressure in damp or humid atmospheric conditions. Fourth, air is more efficiently pulled than pushed. A weatherproof exterior-mounted fan will extract air better as well as isolate the noise. Intermediate in-line duct fans are a second best. Worst are the old-fashioned noisy indoor ceiling propeller fans.
Very quiet efficient inline fans cost three or four hundred dollars. Most will accept variable-speed controls, another nice feature. Panasonic makes an especially nice line of them. More ordinary bathroom quiet fans in the 200 CFM range, for wall or ceiling mount, are about half that price. The idea with a speed-control fan is that you can run it low most of the time, then boost the CFM when mixing nasty chem, or when fighting greater hydrostatic pressure during wet weather. 100 CFM is generally too small to be realistic. Broan probably still has a selection of outdoor-mounted pull fans, which provide more CFM for less money.
Among the many things our company sold to construction before I retired were thousands of ventilation fans a year. Even though darkrooms were a minor percentage of that, I consulted on many darkrooms every year, all the way from tiny bathroom conversions to huge industrial labs using ventilation fans so large that they required three-phase motors. A good placed to review options is a Grainger catalog (their website is so-so). Forget the toy stores like Lowes or Home Cheapo. Nobody in those places has a clue about any of this.