Nitrocellulose Film Hazards in Conservation

By Angela Babin, M.S.



Introduction

       Cellulose nitrate film, more familiarly known as

nitrocellulose, became popular in the late 1880's because its

physical properties made it ideal for photography.  At first,

cellulose nitrate film was used mostly for still photography, but

it was also used for x-ray film and motion picture film into the

early 1950's.  Museums and photographic archives are often faced

with the problem of safety in handling and storage of nitrate

film.  

       In 1988, the National Fire Protection Association (NFPA),

published NFPA 40, the Standard for Storage and Handling of

Cellulose Nitrate Motion Picture Film.  This code doesn't cover

x-ray film.  The NFPA has produced documents for nitrocellulose

film since adoption of the first standard in 1919.  Because

manufacture of nitrate film was stopped in 1951, it was debated

whether to suspend regulation on such film in 1979.  It was

decided that because of the large quantities of cellulose film

stored in archival collections, the standard was still relevant. 

NFPA 40 also addresses projection room requirements for handling

of nitrate film, and also specifies construction and arrangement

requirements for buildings.



Flammability

       Cellulose nitrate film is highly unstable and presents a

very serious fire risk.  It burns quickly with an intense flame. 

The rate of combustion for cellulose nitrate film is about 15

times that of wood.  In the early days of the motion picture

industry, movie houses and even film studios had devastating

fires with many fatalities.  Dry cellulose nitrate can explode

when subjected to heat or shock.  While decomposing motion

picture film has been known to self-combust, still-camera

negatives.has not.  Cellulose nitrate contains chemically

combined oxygen in sufficient amounts to allow burning and

decomposition without the presence of air.  

       Toxic and flammable gases formed during burning or

decomposition may be produced so rapidly that dangerous pressures

may occur in building structures.  The burning of cellulose

nitrate film releases highly toxic gases, including nitrogen

oxides and carbon monoxide.  In one fire, these toxic gases were

responsible for the deaths of 125 people not directly exposed to

the fire.  Since 1951, motion picture film has been produced with

a "safety"  base of cellulose acetate or other slow burning

esters or polyesters.  The fire hazards of these materials are

similar to those of thick paper.  When these films burn, there is

no release of toxic nitrogen oxides. 

Lower levels of heat will result in damage to "safety" film than

to paper records, therefore special protection is needed to

prevent fire damage.  



Health Risks

 Cellulose nitrate film decomposes over time to release toxic

nitrogen oxides.  These toxic gases are skin, eye and respiratory

irritants, and have poor odor warning properties.  Chronic

exposure to the decomposition products of nitrate film,

especially nitrogen dioxide, can lead to headaches, blurred

vision, loss of appetite, emphysema and other systemic damage. 

In the presence of water, these gases can form corrosive acid

gases.  These acid gases can lead to damage of other photographs

and metal corrosion. 



Recommendations

 The decomposition and flammability of cellulose nitrate film 

makes the immediate identification, and proper disposal of this

film necessary, while also preserving the materials stored with

nitrate film.  Although some still photographic negatives have

the word "nitrate" printed along one edge, many nitrocellulose

film negatives are not marked.  Nitrate film should be stored in

accordance with NFPA 40 - Standard for the Storage and Handling

of Cellulose Nitrate Motion Picture Film.  Below will be a

summary of the NFPA's reccomendations.  



Construction Requirements

 The NFPA gives specific requirements on the type of construction

required for buildings and laboratories that handle and store

nitrate film.  Buildings must be of Type I construction (see NFPA

220, Standard on Types of Building Construction).  All rooms in

which nitrate film is stored or handled shall be separated from

each other by partitions that are continuous and securely

anchored, and openings through these must be fire doors that meet

the standards of NFPA 80.  There must be two exits and adequate

aisle space.   Projection rooms, rewind rooms and rooms in which

the stored amount of nitrate film is less than 20 rolls, are

exempt from specific explosion venting requirements.  

       The NFPA requires at least 35 sq ft of floor area for each

worker in inspection rooms, and no more than 15 people may work

in room where nitrate film is handled.  Tables, racks, electrical

equipment, heating equipment and duct systems should comply to

the specifications detailed in the standard.  



Fire Protection

 Except for motion picture projection room of booths or rewind

rooms, every room in which nitrate film is handling quantities

greater than 50 lbs should be protected by an approved automatic

sprinkler system.  Other areas than film cabinets and vaults may

use either an automatic sprinkler system or a deluge system that

has fixed nozzles or open sprinklers.   There are regulations on

the water supplies for sprinklers.   Every room where nitrate

film is used or stored should have portable fire extinguishers

with water or water solutions.  



Nitrate Film storage

       The NFPA standard specifies the allowable amounts of nitrate

film that can be stored.  25 lb (5 standard rolls) to 750 lb (150

standard rolls should be stored in approved cabinets or vaults. 

Amounts over 750 lb must be stored in vaults.  Archival film

should be stored in archival cabinets or archival vaults.  

       Film cabinets, film vaults, archival vaults, and archival

cabinets are restricted in terms of ventilation, construction,

materials, sprinklers, and dimension in accordance with the

standard.  

       Handling of nitrate film also requires particular care.  The

NFPA specifies that all nitrate film must be kept in closed

containers unless being worked on or examined.  These containers

may be individual metal cans for each roll.  Those containers

approved by the U.S. Department of Transportation (DOT) for

shipment are particularly suitable.  Film should not be placed in

such a way, that sprinkler discharge would be hindered; for

example underneath benches or tables.  

       Scrap film must be kept separate from paper waste, scrapped

safety film and other rubbish.  Nitrate film to be discarded

should be collected daily from the work area, and removed to a

unused room.  Safe storage of the scrap film includes storage

under water in steel drums or tightly closing metal containers. 

A storage vault can also be used.  Scrap nitrate film should be

disposed of frequently.  Nitrate film should never be baled or

burned.  The DOT regulates transportation of nitrate film.  



Projection Rooms and Special Processes

       Motion picture projection rooms are especially regulated,

with specifications for fire resistance, enclosures, exits,

openings, all shelves, furniture and fixtures, ventilation, and

lighting.  Processes like splicing, cleaning, repairing,

cataloging and marking may be done in common work areas, but not

in rooms where other operation are performed.  The authority

having jurisdiction shall be consulted to determine the necessary

protection for safeguards against hazards involved with doing

special processes.  These are the types of activities that

archivists, conservators, and museum personnel are often involved

in .  Below are some general health and safety guidelines.  



1) All cellulose nitrate motion picture film and decomposing film

should be copied disposed of immediately according to the local

fire code, and NFPA regulation.  Never incinerate nitrocellulose

film.  A sign of decomposition is when the emulsion becomes soft

and tacky.

1) Only negatives in good condition should be kept.  Nitrate film

in good condition can be stored in acid free, buffered paper. 

Duplicate cellulose nitrate negatives and properly dispose of the

original negatives according to the local fire code, NFPA and the

DOT.  Duplication of nitrate film can be done in two ways.  The

first option is to strip the emulsion from the base and transfer

it to a new and stable support.  This method is only useful for

negatives whose decomposition has not affected the gelatin

emulsion layer.  Alternatively, copy the negative onto

duplicating film and provide negatives from which prints can be

made.  In both cases, before the original film is discarded, be

sure to inspect the duplicate carefully and approve its quality.

2) Store cellulose nitrate film in a cold room where temperature

and relative humidity can be carefully controlled.  A suggested

relative humidity is 35 per cent.  Ventilation must conform to

NFPA regulations.   

4) When handling nitrocellulose film, wear neoprene or buna-N

gloves.  If there are signs of decomposition, wear goggles as

well and provide local exhaust ventilation consistent with NFPA

regulation.  The hazardous decomposition by-products of nitrate

film have poor odor warning thresholds.

5) Because all the hazards associated with nitrocellulose film

increase with age, it is imperative to address safe storage and

conservation before deterioration prevents conservation.





(c) Copyright Center for Safety in the Arts 1991