NBSIR 74-590

A Study of the Feasibility of

Establishing Generic Environmental

Test Parameters for all Consumer

Products

Samuel D. Toner

Product Systems Section

Product Engineering Division

National Bureau of Standards

Washington, D. C. 20234

March 1975

This is a final report.

Prepared for Consumer Product Safety Commission

Washington, D. C. 20207

NBSIR 74-590

A STUDY OF THE FEASIBILITY OF

ESTABLISHING GENERIC ENVIRONMENTAL

TEST PARAMETERS FOR ALL CONSUMER

PRODUCTS

Samuel D. Toner

Product Systems Section

Product Engineering Division

National Bureau of Standards

Washington, D. C. 20234

March 1975

This is a final report.

Prepared for Consumer Product Safety Commission

Washington, D.C. 20207

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts. Director

A study of the feasibility of developing test parameters for the

behavior of consumer products under simulated or actual environmental

conditions was conducted. This report constitutes a discussion of the

results of this study. "Environmental," in this context, means those

conditions to which the product might normally be exposed; for example,

temperature, humidity, ultraviolet radiation, or weathering. Tliese

conditions may be static or cyclic, and may occur individually or in

combination.

The initial purpose of this project was to establish a series of

generic environmental test parameters applicable to all types of consumer

products, which as a result of prolonged exposure to certain environmental

conditions, would become hazardous.

A consumer product was assumed to be one normally used in an individual household. It was reasonable to assume that no individual

product would be subjected to constant environmental conditions throughout its useful life, and that some products are intended to be used

exclusively indoors, others exclusively outdoors, and others both outdoors and indoors.

Products which can become hazardous as a result of environmentally

induced failure can be classified into two general categories, those

which exhibit no change in parameters such as temperature, moisture

content, etc. in use, and those which in normal use assume conditions

not present during storage environments.

When this program was begun, it was realized that the proposed

scope was too broad. It was obvious tliat certain limitations to the

scope would be necessary if a reasonable approach to the problem of

generic testing were to be achieved. Consequently, the test parameters

selected for study were limited to the evaluation of products in the

quiescent state, i.e., neglecting the fact that at various times during

its useful life a product exposed to and preconditioned in a specific

environment might be subjected to conditions that were totally irrelevant

to the ambient conditions under consideration. For example, certain

elements of a product might on becoming functional be rapidly subjected

to temperatures hundreds of degrees above any normal environmental state.

Thus, it was clear that any attempt to establish environmental test

procedures involving all of the ramifications that would include all

possible variants between product and environment would yield an unworkable number of test parameters. Consequently, the effects of normal use variants on the functional stability of a product were not included in

this initial study.

Although the combined effects of functional use cycles and

environmental conditions were excluded from this study, it was recognized

that for a given product a hazard might not occur during exposure to

various environmental storage conditions in the quiescent state. However,

the problems involved in simply attempting to establish generic environ-
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mental test parameters to cover all potentially hazardous products

were enormous. Obviously the inclusion of functional cycles in a series of environmental test conditions would have to be based on the

individual product and simulate as well as possible the conditions to

which the product would be subjected in use.

In some cases environmental test procedures might be of little

value unless associated with mechanical, physical, and chemical test

procedures (exclusive of functional use cycles) in order to determine

whether slow deterioration was occurring to the materials or components

that would eventually render the product unsafe. Thus, tests of this

type cannot be of a generic nature, but must be specifically selected

to evaluate the materials and components in question. Some exceptions

may occur. For example, a power tool associated with seasonal use may

be subject to environmental extremes during long term non-use storage

that would be basically irrelevant to the conditions encountered during

use. In such cases tests to detect onset of safety deterioration might

be expected to be used only in conjunction with cyclic test parameters

typical of the environmental conditions encountered in use rather than

those encountered during long term quiescent storage.

Of particular concern in this study were the types of failure

modes that produce hazards due to adverse environmental conditions.

The first phase of the study concerned an evaluation of injury surveillance data as a means of determining tlie types of environmental exposure

test conditions that should be established. Data of this type may not

indicate whether the injury was due to failure of the product, or the

failure mode which produced the hazard. If the type of failure is

described, or can be deduced, the cause of failure normally is not

stated and is frequently unknown. Consequentially, it becomes difficult

to determine the factual cause of failure, e.g. environmental deterioration, or mechanical failure due to normal wear or improper maintenance.

When a hazard producing failure occurs and results in an injury

which is subsequently recorded in the surveillance data, it is possible

to predict the approximate number of similar product related injuries

that may occur in a specified period of time. However, there may be

other instances of identical failures resulting from environmentally

induced deterioration of the product, in which no injury occurs due to some fortuitous circumstance, such as the user's ability to recognize

the inherent danger. It appears that under the present system of information retrieval, data on the latter type of potentially hazardous product

failures would be available from the manufacturer or distributor only

if appropriate records are maintained on returned items. However, data

of this type might only be available for those products that were still

under warranty, were repairable, or whose cost of repair was sufficiently

low so that the owner would not discard the product.
3

The listing of consumer products contained in the complete

NEISS Consumer Product Hazard Index was evaluated in order to determine

those products which could be expected to deteriorate due to environmental exposure conditions, and capable of resulting in an injury

producing failure. Many of these products were associated with the

higher AFSI values reported in the Index. For convenience the individual

products were grouped into pertinent general product categories. Some

typical categories which include a majority of potentially hazardous

products, divided into areas of primary intended use, are as follows:

Indoor Products Outdoor Products

Sports and recreation equipment

Structures and materials

Yard and garden tools and equipment

Small appliances

Major appliances

Communication equipment

Entertainment appliances

Children's furniture

Home furnishings

Structures and materials

Workshop equipment

it is obvious that the above products involve the use of a wide variety

of materials and fabrication and assembly techniques.

A search of Federal and National Standards did not provide much

assistance in the development of generic environmental test parameters

that would be applicable to all of the product categories listed above.

Most specifications and testing procedures are oriented towards basic

materials and usually require test specimens of predetermined dimensions,

and specific types of testing instrumentation. Frequently, the specimen

configuration is not representative of that found in the end product,

and the instrumentation may not be amenable to testing the entire product.

Assuming that most products are composites and assemblies it is possible

that if a failure mode can be associated with a specific component or sub-assembly then test procedures for these specific items, rather than

the complete product might be developed. When appropriate basic materials

standards are available they may be used to specify the requirements for

the material used in such a component. On the basis of the small amount

of data commonly available on product related injuries, it seems reasonable to suspect that many hazard producing failures may be due primarily

to some inherent fault in the product such as poor design or selection

of an inadequate material. Although in the latter case, materials

standards may serve as the basis for selection of a more appropriate

material, this often results in an increase in cost of the product.

The evaluation of some products may require only the use of a relatively simple combination of environmental parameters, such as temperature and humidity cycling at simulated indoor conditions.

Products intended for infrequent outdoor use may have to be evaluated

for resistance to greater temperature extremes, sunlight, rain, wind
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erosion, industrial fumes, etc. It is obvious that in most cases these additional test parameters would only add to the complexity of

the testing problems. Another problem arises for those products

which while functioning normally undergo a transformation that drastically alters the conditions induced by the environment; for example,

a rapid rise in temperature of the product. Probably some products

of this type should be subjected to dual test procedure, one in which

it remains quiescent, and one in which it would become functional at

specified intervals and conditions. Regardless of the types of

environmental parameters to which a product is subjected, if the results

are to be of value, the product undoubtedly will need to be subjected

to one or more mechanical, physical or chemical tests in order to

determine whether slow deterioration of properties is occurring that

would result in an unsafe product. Such limitations would necessarily

require each product or product design to be evaluated on its own merit regarding its resistance to failure. In order to be of significance such an evaluation must take into consideration the intended use,

probable location and duration of use, the types of materials used,

and the assembly techniques used. The simulated environmental test

program could be developed for obtaining a reasonable degree of

certainty that failure of the product would not result in a potentially

injurious hazard. However, it must be recognized that many simulated

test conditions do not exactly match those encountered in normal

service. Consequently in developing a test procedure it is reasonable

to increase the severity of the tests.

A thorough study of the types of failure occurring in a given

product would provide information that would be extremely useful to

the design and materials engineer, and for developing means that

would lead to the elimination of a recurrence of the failure. A

study of the degree of usage, distribution of usage, and the relationship of these factors to the ratio of injuries occurring could be

the basis for, and act as an aid in, the selection of the most

appropriate environmental test parameters.

In conducting environmental tests in the laboratory it is

generally considered wise, if practical, to exceed the conditions

to which a product might normally be expected to be exposed during

its service life. By using limited increases in severity in laboratory testing, particularly when performing cyclic tests, potential

failure modes due to the selection of materials, design criteria,

etc., may be more readily identifiable. Nevertheless, environmental

laboratory tests often do not simulate all of the parameters to which

a product may be exposed. Therefore, increasing the severity of

tests which do simulate environmental conditions may offset the

inability to duplicate certain conditions. For example, no reference

could be found for a standard laboratory test procedure that simulated

the effects of industrial fumes and airborne particulate matter,

which frequently may result in an increased rate of deterioration

particularly in conjunction with other weathering factors such as sunlight and rain.
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When consideration is given to the wide variety of materials and

types of construction used in various products, it is evident that the

usual standardized test procedures are inadequate. These, which are basically concerned with a single material or construction, would rarely

predict a product malfunction due to basic differences in the response

of dissimilar materials to various environmental situations.

A standard test procedure intended primarily for use in the

evaluation of a single material or a simple composite may require some modification when adapted to the testing of an end product, if the

standard procedure involves the subjecting of the product to conditions

that are abnormal to its intended use. Thus, the effect of elevated

temperature on a fabricated component may be more severe than it would

be on a carefully prepared laboratory test specimen. As an example,

a molded thermoplastic material may be unaffected by test temperatures

up to 70-75°C (158-167°F), but if exposed to a temperature of SS^C

(185°F) in order to accelerate the effects of temperature, might rapidly

distort and result in a hazardous condition. Thermally induced distortion is usually related to the temperature at which the plastic was cooled after molding and may occur at a much lower temperature than

that of the distortion temperature required for a laboratory prepared

test specimen made in conformance with a basic standard specification.

With some materials accelerated cycling between two different relative

humidities may not approximate actual exposure conditions due to the

inability of the material to equilibrate rapidly at each extreme of the

test cycle. Materials which are hydrophobic by nature may require

several days, or more, depending upon thickness and area of exposure,

for the moisture content to become fully equilibrated with the surrounding atmosphere.

One proposed criterion for the study was the establishment of

environmental parameters which simulate those encountered in geographic

regions of the country. When the possibility of developing such

environmental test parameters was considered, based primarily on atmospheric conditions, i.e., daily mean temperatures, daily high and

low temperatures, variations of relative humidity, average monthly

high and low temperatures, hours of sunlight and rainfall, it appeared

that very few products would fall solely into a regional category.

In evaluating mean temperature data of various areas of the country,

for example, there did not appear to be much variation between northern

and southern latitudes, with the possible exception of Alaska. It is

well known that the number of days and the portions of each day in

which the maximum and minimum extremes of temperature occur may vary

considerably from one geographic location to another. Nevertheless,

many products are distributed on a nationwide basis. In some regions,

topographical variations may cause as great a difference in some climatological conditions, as those occurring over large intraregional

distances. Therefore, it appeared that an approach based on regional

environmental conditions would lead to unwieldy test parameters. Consequently, it was felt that generic types of environmental test conditions
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could be adapted realistically to a given type of product regardless

of geographic location of use. However, regionality could result in

a variable ratio of product to population. With these points in mind,

it seems that a reasonable approach to environmental cycling tests

would, as in the case of variations in temperature and relative humidity,

involve a number of cycles between high and ambient temperature at

various relative humidities, followed by similar cycling between ambient

and low temperatures, to separately simulate exposure to summer and

winter conditions, respectively. This would minimize thermal shock

effects such as might occur in alternate cycles of high and low temperatures, but to which the product might never be exposed in actual use. However, the technique of rapid cycling between high and low temperatures,

for the express purpose of inducing thermal shock, may be advantageous

with regard to accelerated test procedures: an example is the testing

of products consisting of composites in which various components consist

of or are fastened together by materials having distinct differences in

their coefficients of thermal expansion.

An example of the problems that can occur in attempting to establish

generic environmental test conditions is as follows. A product intended

for indoor use only might only need to be subjected to cycling tests

between two specified temperatures, for example, 25°C (77°F) and 60''C

(140°F), while being simultaneously subjected to various relative

humidities, for example, 20, 50, or 90"o. There are at least nine

different combinations between these two temperature extremes and three

relative humidity percentages depending on whether the R.H. remains

constant, increases or decreases with rise in temperature.

Artificial weathering devices may vary in their ability to

simulate or accelerate degradation compared to how it would occur under

natural weathering conditions. Frequently the major determinant

governing the effect of these devices is directly associated with the

composition of the material undergoing test. Variations may also

occur as a result of the availability of a choice of the light source

(carbon-arc. Xenon-arc) and the test c>cle used, e.g., light only,

light plus light/water spray, or either of these in combination with

a dark period.

Similar choices of test conditions occur in the simulation of

other types of environmental conditions. Usually the most appropriate

test conditions are determined by the type of material being investigated.

When the addition of an operating cycle of a product results in

a change in its conditioned state at any part of a test cycle, the

complexities involved in attempting to establish a set of environmental

test parameters capable of use on all products susceptible to hazard

producing failures is readily obvious.
In conclusion it is apparent that no single set of generic

environmental conditions would provide a completely adequate means

of assessing their effects on all types of consumer products subjected

to environmentally induced, potentially hazard producing failures.

Nor does it appear that limiting a proposed set of conditions to a specific region would in any way decrease the complexity of such

testing procedures.

It may be possible to establish some broad general limits for

parameters such as temperature, relative humidity, ultraviolet exposure,

etc. , which might be applicable as a first approximation in establishing design criteria for a specific product.

However, it seems that it will be essential to limit environmental testing to only those parameters appropriate to a specific

product, or to a limited series of comparable products normally

exposed to similar environmental conditions. This could result in

the need for a comprehensive analysis of the potential failure modes

of each type of product, followed by a selection of arbitrary parameters

most likely to induce failure during the expected service lifetime of

the product. Such parameters would necessarily have to be based on both the materials used and the methods of construction or assembly

used to produce the end product.

use OMM-NBS-OC
NBS-114A (REV. 7-71)

U.S. DEPT. OF COMM.

RIRI lOriRAPHir DATA

SHEET

1. PL'HLK A HON OK Kl-POK 1' NO.

NBSIR 74-590

2. Gov't Aciession

.NM,.o. 3. Recipient's Accession No.

4, TITLE AND SUMTITI.I- A Study of the Feasibility of Establishing Generic

5. Publication Date March 1975

6. Performing Organization Code

7. AUTHOR(S)

Samuel D. Toner

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 4460504

11. Contract/Grant No.

12. Sponsoring Oganization Name and ( omplcu- Address (Street, City, State. ZIP)

Consumer Product Safety Commission

Bethesda;, Maryland 20016

13. Type of Report & Period Covered

Final

14. Sponsoring Agency C^ode

15. SUPPLEMENTARY NOU S

16. AFHSTRAC 1 (A 2()0-word or less factual summary of most sigfiificant information. If document includes a significant

bibliography or literature survey, mention it here.)

A study was conducted to determine the feasibility of establishing a set

of generic environmental test parameters that would be applicable to all types

of consumer products, with a potential for developing injury producing hazards

as a result of environmentally induced failure. It was concluded that this

approach is not a practical one. It is apparent that the safeness of a product

or type of product should be determined on the basis of simulated environmental

tests appropriate to its specific end use.

17. KEY WORDS (six to twelve entnrs, alphabetic al order, capitali ze only the first letter of the first key word unless a proper name, separated by semicolons ) Environmental tests; product safety

18. AVAlLAiULn Y ^Unlimited 19, SECURITY CLASS

(THIS REPORT)

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