Tom Benjamin 

Iron Mountain Film & Sound Archives

“Environment Trends for Motion Picture Preservation”

September 29, 1999

Orphans I at the University of South Carolina


Based on my experience with one of the largest film and document storage operations in the world, I will discuss some of the opportunities and challenges of storing motion picture film, in particular storing film underground.  The degree of security afforded the motion picture films is one of the most important considerations to be made when choosing a site to store film material, whether it is on-site or off-site.  Nothing else will matter if something happens to your important material, and a visit of your security installations could be the most important and best investments you ever make.  The American National Standards Institute proposes that we store black-and-white film at 36 to 45 degrees Farenheidt and color film even colder than that.  Our company doesn’t specifically recommend environmental conditions to our clients.  That gets risky from a liability stand point, but this much I can tell you, that in the fourteen years that I have been there, colder and drier is better.  It seems to be getting even colder and drier, the conditions that film preservation experts and clients want.

I work underground in western Pennsylvania.  The majority of the underground facilities that are located across the country are in mines.  Those include iron ore mines and salt mines.  Ours is a limestone mine.  Underground storage first became attractive as an indirect result of the Cold War.  The Russians had the bomb.  We had the bomb, and folks were concerned about nuclear attack.  The massive underground structures built as refuges from nuclear fallout are now being retrofitted for new purposes, including film vaults.

There are a number of opportunities  for underground storage in addition to motion picture film.   We store microfilm, microfiche, reels of computer tape.  We have miles and miles of magnetic media. We have over 2 million cartons of paper records.  Underground at our facility we have approximately 1,000 people working underground in our storage facility.  In addition to inactive storage, we have fully operational data centers located there.  And we have some offices.  In the office locations,  a lot of these folks have their entire business operation needs to be kept safe and secure. This facility is 220 feet underground.  The main entrance is through a three-ton steel gate.

Why underground?  The biggest advantage has to with the high level of physical security.  There is one way in and one way out (that we advertise and promote).  Access is controlled by an alarmed gate and armed guards 24 hours a day, seven days a week.  The underground facilities are virtually immune from natural and man made disasters –- fire, flood, theft, civil disorder, hurricanes.

Earthquakes?  Let’s talk about earthquakes.  We store assets for five of the major Hollywood film studios.  Visitors from Hollywood want to talk about earthquakes.  So these folks are somewhat preoccupied by the subject.  In selecting an underground facility, it would be best to choose one that is in a low incident of earthquakes.  We are in Pennsylvania, right where it says zero, and I work underground everyday, so we have just as high a likelihood of having an earthquake there as they do in Florida or in Texas, as you can see.

Another principal reason for underground has to do with maintaining the proper climate conditions.  It is really very easy for us to maintain the temperature and the relative humidity storage conditions that are required for the long term preservation of the material.  The first thing we need to do is to identify the storage conditions that we are shooting for.  We segregate the various types of materials that we would store.  Magnetic media – keeping it separate from paper – and keeping it separate from motion picture film.  For the motion picture film, as I mentioned before,  we selected ANSI IT.  Some of our clients will maintain their material at 60°F, others will choose 55° and 35% RH.  We have space maintained at 45°, 40°, and 33°F, and we are working with a client now for 0° F.  So, it is not difficult for us to maintain those conditions underground.  With standard HVAC equipment we are able to maintain about 55° to 60° temperature.  To get any lower than that, we need to use refrigeration equipment and obviously, the size of the HVAC equipment depends on what the moisture and heat loads are.  Factors include the number of people in the facility, the service activities, service levels.  But because we are underground, we are not subject to seasonal  changes.  In our area of the country, the outside temperature can vary by over 100° from summer to winter, and the relative humidity can vary by more than 50%.  The underground environment  is a constant 58° and 85% relative humidity.  

This is a map of our facility.  Just the portion we have developed is about 133 acres underground, and the entire mine – people often ask what about when it fills up? – the mine is 1000 acres.  So, I am not going to be here when it fills up.  We are occupying about 10% of what the capacity is.  What we able to do is to segregate the space., the developed space from the undeveloped space by building separation walls.  Mounted in these walls are huge industrial mine fans.  We circulate about 250,000 cubic feet of air a minute out the entrance.  The entrance is located right here.  So mounted in the exterior walls are these industrial mine fans.  The air is brought in from the outside and then forced all out that entrance.  What we do is to bring the air in from the opposite side of the mountain, It comes across the 20-50 foot thick rock walls, and in the summer, the rock walls act as a huge heat sink.  It absorbs all of this heat, and by the time the air gets to the mine fans here, it is at a nice 55°.  In the winter the opposite happens.  We are pulling in air from the outside, could be 20°. Once again, we move it across those rock walls.  It then increases the temperature, and once again, we still get 55° coming in through there.  So it is a great system, and it is virtually free.

In order to get the 85% RH down, we’d need to use desiccant dehumidification equipment.  Once again, we need to look and see the size of the facility.  We have facilities that are the size of this room.  We have others that are the size of this particular floor of the building.  Our engineers would use psychometric charts to determine the size of the dehumidifiers needed to insure that they are capable of removing the proper amount of water vapor.

We use a modular approach to our HVAC equipment.  The first approach is to use the cool mine air that we talked about and a small commercial dehumidifier, such as the one I have shown.  For colder conditions we would use a regular commercial air conditioning unit, and for still colder, we might use a small refrigeration unit.

Another advantage to underground has to do with fire protection.  This is a picture of a small vault.  We use the existing rock walls that you can see along the back.  Wherever possible we would use an existing rock wall.  These walls are about 20 – 50 feet thick of solid rock, and what we do is to compartmentalize as best we can these individual vaults.  Here is a picture down the hallway, and as you would just walk down, they look like individual hotel rooms to the left and to the right.

Fire suppression is also relatively easy.  This is a shot of the ceiling where we have smoke detectors.  Many of our facilities would have either dry pipe or wet pipe sprinkler systems, like this 1301 Halon Fire Suppression System [Figure #].  We have on-site our own fire brigade with several fire trucks.  We tested the response times of public fire fighting units, but being in a rural area, we found them too long. 

Another advantage:  underground construction costs are relatively inexpensive.  We start with an area, we looked before at the mine map, we started with the shell of the building.  What we do is to take some of the rooms.  On average they run about 40 feet wide, about 600-700 feet long, and the ceilings are about 14-16 feet high.  We select a site, a construction crew goes to work with a pick, and they work for quite a while.  So they will remove as best they can any  loose stone.  We will work on the walls, we will work on the roof to insure there is nothing loose that is left over from the days of the mining era.  Where needed we would build separation walls.  So, if we had a room this size and perhaps a c???

also some challenges.  Even though you are underground, insulation is always recommended, especially when commercial refrigeration equipment is installed.  It just makes financial sense.  The environmental conditions of the surrounding space, the temperature and the relative humidity need to be considered, depending on what the temperature and RH is you are shooting for internally.  This drawing is a schematic, and you should have a copy of that in your packet.  It just outlines the concrete block wall, the phone insulation and wall board on the outside, and depending on how cold you are looking to design the space, whether it is 1” or 3”.  We have some 4” and  6”  insulation.

You also need to consider a vapor barrier.  A good vapor barrier is important if you are hoping to maintain the proper storage specifications and operate your HVAC system economically.  Epoxy paint is important, and also a plastic barrier is important.  You don’t really want to underestimate the vapor pressure.  It has been known to peel paint off of walls.  You need to keep a positive pressure, so  within the facility you want to make sure that you are pumping more air from the outside and conditioning it.  The higher pressure inside the room than outside helps control the dust and also insures that there isn’t a build up of contaminants within the room itself.  We have used this weather stripping.  The space inside where Bev is standing is about 33°, outside this room is just a small 100 square foot anti-room.  The temperature there is about 50°.  What we do is take the material from in the storage vault, bring it out to the anti-room where it will sit for about a day so it can climatize before we take it out and ship the material back to the client.  So these environmental door seals are very, very helpful.

Construction and maintenance of all of this equipment can also be a challenge.  We do our own construction.  These fellows are standing up on a wall.  These are two man crews.  These are not the fellows you want to arm wrestle at the company picnic.  One fellow will stand there with a wedge and the other will hit it with a 15 – 20 lb. sledge hammer, and they will do that all day long.  So we insure that every single square foot over head is solid rock.  Underground we allow vehicles.  We have at any point and time 25 –30 vehicles traveling underground. 

As far as air quality is concerned, we tell folks it is best to pick a place that has no air contaminants.  We bill it as ‘remote but accessible’.  So air contamination can be solved by two different methods, dilution or filtration.  We use both.  By dilution we mean to move a large volume of uncontaminated air.  We remove any airborne impurities that are introduced by the storage media themselves.  Many clients send us acetate-based material.  Obviously, if they are interested in storing it at 35°, it will be susceptible to “vinegar syndrome.”  We use impregnated charcoal filters to remove some of the acids from the air and keep those levels low.  The best way to insure that you are doing a good job is to have the air quality tested by a laboratory. 

Additionally, at our facility we have five emergency diesel power generators. Emergency power is critical.  It really puts a lot of stress on the film if you are storing material at 35°, and all of a sudden you turn the power off for a week and a half.  So we are able to maintain our own emergency power units.  The longest we have ever been without power is about 18 hours, and the generators certainly were more than capable of maintaining power for those conditions.  As you can imagine, with 1,000 people underground turning the lights out is just not an option.


-- Tom Benjamin