Final Report on Formaldehyde Levels

in FEMA-Supplied Travel Trailers, Park Models, and Mobile Homes

From the Centers for Disease Control and Prevention

July 2, 2008

Amended December 15th, 2010
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers i

Table of Contents

Executive Summary....................................................................................................................... iii

Background......................................................................................................................................1

CDC Testing of Occupied Trailers..............................................................................................1

Formaldehyde Exposure in Residential Indoor Air .....................................................................3

Health Effects...............................................................................................................................4

Regulations and Standards of Formaldehyde Levels...................................................................5

Objectives ........................................................................................................................................5

Methods............................................................................................................................................5

Study Personnel.................................................................................................6

Trailer Selection...........................................................................................................................6

Eligibility Criteria ........................................................................................................................7

Informed Assent and Consent and Human Subjects Protection ..................................................7

Variables......................................................................................................................................7

Exposure Assessment Questionnaire ...........................................................................................7

Environmental Walk-Through Survey.........................................................................................8

Formaldehyde Sample Collection................................................................................................8

Temperature and Relative Humidity Sample Collection.............................................................8

Sample Collection Data Sheet .....................................................................................................8

Data Collection, Entry, Editing, and Management......................................................................8

Statistical analysis........................................................................................................................9

Results..............................................................................................................................................9

Participation Rates.......................................................................................................................9

Overall Range and Variability of Formaldehyde Levels...........................................................10

Occupant Activities....................................................................................................................10

Trailer Characteristics................................................................................................................10

Walk-Through Survey ...............................................................................................................10

Multivariate Analysis.................................................................................................................10

Discussion......................................................................................................................................11

Limitations.....................................................................................................................................12

Conclusions....................................................................................................................................13

Recommendations:

 Recommendations for Public Health, Emergency Response, and Housing Officials...........13

 Recommendations for Residents Awaiting Relocation..............................................14

 Further CDC Action......................................................................................14

References .....................................................................................................15
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers ii

Figure 1.........................................................................................................18

Figure 2.........................................................................................................19

Figure 3.........................................................................................................20

Figure 4.........................................................................................................21

Table 1..........................................................................................................22

Table 2.........................................................................................................23

Table 3.........................................................................................................24

Table 4.........................................................................................................25

Table 5..........................................................................................................28

Table 6.........................................................................................................30

Table 7.........................................................................................................30

Table 8.........................................................................................................31

Table 9.........................................................................................................32

Appendix A. Protocol For Trailer Selection and Recruitment ................................................33

Appendix B. Phone Log for Participant Recruitment .............................................................35

Appendix C. Obtaining Assent................................................................................................39

Appendix D. Informed Consent for Participation...................................................................40

Appendix E. Exposure Questionnaire and Walk-Through Survey .........................................43

Appendix F. Environmental Sampling Protocol.....................................................................49

Appendix G. Sample Data sheet for Formaldehyde, Temperature, and Relative 

Humidity Data Collection................................................................................54
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers iii

Final Report on Formaldehyde Levels

in FEMA-Supplied Travel Trailers, Park Models, and Mobile Homes

From the Centers for Disease Control and Prevention

July 2, 2008

EXECUTIVE SUMMARY

In December 2007 and January 2008, the Centers for Disease Control and Prevention 

(CDC) measured formaldehyde levels in a stratified random sample of 519 FEMAsupplied occupied travel trailers, park models, and mobile homes (i.e., “trailers”). At the 

time of the study, sampled trailers were in use as temporary shelter for Louisiana and 

Mississippi residents displaced by hurricanes Katrina and Rita. The study aimed to 

determine formaldehyde levels in occupied trailers, determine trailer characteristics that 

could affect formaldehyde levels, and provide information to assist FEMA in deciding 

whether to relocate residents from FEMA-supplied trailers in the Gulf Coast area. This 

study assessed only current formaldehyde levels in the occupied trailers; it was not a 

health effects study.

To evaluate levels of formaldehyde, investigators conducted a 1-hour continuous indoor 

air sample and sample measurements of indoor temperature and relative humidity. To 

determine factors that could affect formaldehyde levels, investigators administered a 

short questionnaire to adult residents about occupant demographics and trailer 

characteristics. To observe the exterior and interior of the trailer, investigators conducted 

a walk-through survey.

In many of the trailers tested, formaldehyde levels were higher than typical U.S. indoor 

levels. The geometric mean level of formaldehyde in sampled trailers was 77 ppb (range: 

3–590 ppb). Formaldehyde levels varied by trailer type, but all types tested had some 

levels ≥ 100 ppb, the level at which health effects have been described in sensitive 

persons.

In this study, travel trailers had significantly higher average formaldehyde levels than did 

park models and mobile homes. A higher proportion of travel trailers than park models 

and mobile homes also had formaldehyde levels ≥ 100 ppb and ≥ 300 ppb. In multivariate 

analysis, factors such as temperature; relative humidity; trailer type and brand; opened

windows, doors, and scuttles; and presence of mold (≥ 1 ft2

) were significantly associated 

with formaldehyde levels.

Because formaldehyde levels tend to be higher in newly constructed trailers and during 

warmer weather, levels measured in this study are likely to underrepresent long-term 

exposures; many of these trailers are approximately 2 years old, and the study was 

conducted during the winter. In addition, the study did not evaluate any specific patterns 

of use with respect to specific types of trailers.

On the basis of the data reported here and in previous scientific reports and publications 

about adverse health effects associated with exposure to elevated formaldehyde levels, 
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers iv

CDC recommended that FEMA relocate Gulf Coast residents displaced by hurricanes 

Katrina and Rita and still living in trailers. Relocation priority should be given to 

occupants suffering symptoms potentially attributable to formaldehyde exposure and to 

vulnerable populations, such as children, elderly persons, and persons with chronic 

respiratory illnesses.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 1

BACKGROUND

On August 28 and 29, 2005, Hurricane Katrina—a Category 4 storm—made landfall on the U.S. 

Gulf Coast between New Orleans, Louisiana (LA), and Mobile, Alabama. On September 24,

2008, Hurricane Rita—a Category 3 storm—made landfall along the Texas-Louisiana border, 

Many families evacuated from the U.S. Gulf Coast region returned later to find their homes 

severely damaged.

Starting in October 2005, the Federal Emergency Management Agency (FEMA) provided 

temporary housing along the Gulf Coast by supplying approximately 100,000 trailers (see box).

In LA, more than 60% of trailers provided to residents were on private property. In Mississippi 

(MS), more than 78% of trailers were on private property. The remaining trailers in both states 

were in FEMA-designated trailer parks.

CDC Testing of Occupied Trailers

From December 21, 2007, to January 23, 2008, the Centers for Disease Control and Prevention 

(CDC) assessed levels of formaldehyde in indoor air of a random sample of occupied FEMAsupplied trailers. Formaldehyde testing was one of several actions CDC initiated in response to a 

July 13, 2007, request from FEMA to investigate concerns about formaldehyde in occupied 

FEMA trailers in LA and MS. This report details only the testing of occupied trailers for 

formaldehyde levels; it was not a health effects study. 
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 2

Definitions for Trailers Used by FEMA

for Gulf Coast Residents Displaced by Hurricanes Katrina and Rita

• Mobile homes are manufactured homes wider than 8 feet or longer than 40 feet (for an area >320 

ft2

). They are built on permanent chassis; contain plumbing, heating, air-conditioning, and 

electrical systems; and are designed for use as permanent dwellings. Mobile homes are defined 

and regulated by the U.S. Department of Housing and Urban Development (HUD).

• Park models are manufactured homes of 320–400 ft2 administratively exempted from HUD 

formaldehyde standards. Park models may be regulated by transportation authorities and by 

manufacturer acceptance of a voluntary American National Standards Institute standard applying 

to their construction.

• Travel trailers are wheel-mounted trailers designed to provide temporary living quarters during 

periods of recreation, camping, or travel. Travel trailers generally have size limits, such as 8 feet 

wide and 40 feet long, for an area <320 ft2

. Travel trailers generally are considered vehicles rather 

than structures and are regulated by state transportation authorities rather than by housing 

authorities. Travel trailers have been used principally for short-term housing needs. They are 

placed on private sites while a homeowner’s permanent residence is repaired or in group 

configurations primarily to support displaced renters.

• Manufactured homes include mobile homes and park models and are used to meet both shortand long-term disaster housing needs. Manufactured homes typically are placed on commercial 

pads or in group sites developed expressly for this purpose.

• “Trailers” in this report refers collectively to travel trailers, park models, and mobile homes.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 3

Formaldehyde Levels in Residential Indoor Air

Formaldehyde in homes is a longstanding issue. Formaldehyde frequently is used in plywood, 

fiberboard, resins, glues, carpets, and several other construction components. In the past, 

formaldehyde also was used in insulation of many homes. In March 1982, the U.S. Consumer 

Product Safety Commission (CPSC) called for a ban on urea foam formaldehyde insulation 

(UFFI) (US CPSC, 1982). Although several commercial groups challenged this ban, citing 

greater formaldehyde exposure from carpets and other building materials, UFFI use had dropped 

precipitously by the mid 1980s. However, homes built before or around the UFFI ban still had 

this insulation.

The 1982 ban on UFFI contributed to the decreased levels of formaldehyde in more recent 

studies. Changes in the type of pressed wood products containing formaldehyde resins or glues 

also contributed to the decrease. In the past, pressed wood products often contained ureaformaldehyde resins. Today these resins are not as widely used. Instead, many pressed wood 

products are constructed with phenol-formaldehyde products (commonly known as exteriorgrade products). Phenol-formaldehyde products emit much less formaldehyde (US EPA, 2007).

Temperature, relative humidity (RH), ventilation, and age of house also contribute to differences 

in measured formaldehyde levels. In longitudinal studies, formaldehyde emission rates were 

nearly constant over the first 8 months after construction, and then began to decline, suggesting 

that formaldehyde off-gassing continues for extended periods but decreases with the age of the 

home (Park and Ikeda, 2006). Studies also show that older homes have lower formaldehyde 

levels than do newer homes (Hodgson et al., 2000; Gordon et al., 1999).

A 1985 U.S. study investigated formaldehyde levels in different types of housing (Stock and 

Mendez, 1985). Formaldehyde levels in 38 conventional U.S. homes averaged 40 parts per 

billion (ppb), with highs of 140 ppb. Nineteen apartments and 11 condominiums had average 

formaldehyde levels of 80 ppb and 90 ppb, respectively, with highs of 290 ppb. A more recent 

study of new homes found geometric mean (GM) formaldehyde levels of 34 ppb in 

manufactured homes and 36 ppb in site-built homes (Hodgson et al., 2000). This study suggested 

that formaldehyde levels in conventional homes have decreased greatly since the 1980s, possibly 

because of decreased use of plywood paneling and reduced emissions from the composite wood 

products used.

The U.S. Environmental Protection Agency’s National Human Exposure Assessment Survey 

found a median formaldehyde level of 17 ppb, with a high of 332 ppb, in 189 Arizona homes 

(Gordon et al., 1999). In a recent study of 184 single-family homes in three cities, Weisel et al. 

(2005) found mean formaldehyde levels of 3 ppb in outdoor ambient air; 17 ppb in home indoor 

air; and 16–25 ppb in trailers.

These studies indicate a trend. Even though all homes have some formaldehyde, levels generally 

seem to have decreased since the early 1980s. Lower ventilation rates in manufactured homes

and greater ratios of surface area to volume may factor in this trend (US CPSC, 1997).
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 4

Health Effects

Symptoms from acute exposure to formaldehyde commonly manifest as irritation of the throat, 

nose, eyes, skin, and upper respiratory tract. This upper respiratory tract irritation can exacerbate 

symptoms of asthma and other respiratory illnesses (Main et al., 1983; Bracken et al., 1985; 

Kilburn et al., 1985; Imbus et al., 1985; Anderson et al., 1979; Garret et al,. 19991; Hendrick and 

Lane, 19771; Institute of Medicine, 20001; Jaakkola et al., 20041; Kryzanowski et al., 19901; 

McCoy, 20081; NHLBI et al., 20071; Nordman et al., 19851; Rumchev et al., 20021; Staab et al., 

20081

; Thompson and Grafstrom, 20081).

Acute and chronic health effects of exposure to formaldehyde vary by individual. At 800 ppb,

nearly everyone develops some acute irritative symptoms; however, formaldehyde-sensitive 

persons have reported symptoms at levels around 100 ppb (Main et al., 1983; Bender et al., 1983; 

Hanrahan et al., 19841). Additional studies have found health effects at 100 ppb in sensitive

persons chronically exposed to formaldehyde (Ritchie et al., 1987; ATSDR 20101). Typically 

olfactory recognition occurs around 500 ppb, leaving the average exposure from a home below 

this level. Sensitive and sensitized persons can experience symptoms without detecting odor and 

thus receive little or no warning of exposure (Kulle et al. 1987; Weisel et al. 2005; Fischer et al., 

19951

; Garrett et al., 19991; Kiec-Swierczynska, 19961; Lee et al., 19841; Maibach, 19831; Marks 

et al., 19981

; Wantke and Wantke., 19961).

In addition to acute health effects from formaldehyde, chronic effects in occupational settings 

have been studied. A study of 186 male plywood workers associated formaldehyde exposure 

with several respiratory symptoms, including cough and chronic bronchitis, and suggested that 

formaldehyde exposure induces symptoms of chronic obstructive lung disease (Malaka and 

Kodama, 1990). Funeral home workers reported chronic bronchitis more frequently than did 

controls who were not occupationally exposed to formaldehyde (Holness, 1989).

However, studies attempting to correlate worker-reported symptoms, such as cough or shortness 

of breath, with formal objective pulmonary function testing have shown conflicting results. Two 

studies demonstrated a small and reversible decrease in forced expiratory volume and forced 

vital capacity (Alexandersson et al., 1989; Alexandersson et al., 1982). Additional studies 

employing formal pulmonary function testing demonstrated no significant difference in 

pulmonary function testing parameters (Horvath, 1988; Holness et al., 1989).

The carcinogenicity of formaldehyde has been extensively studied during the last 30 years. In 

June 2004, the International Agency for Research on Cancer (IARC) reclassified formaldehyde 

from “probably carcinogenic to humans” to “carcinogenic to humans.” IARC has concluded that 

formaldehyde exposure causes nasopharyngeal cancer (http://monographs.iarc.fr/ENG/Meetings

/88-formaldehyde.pdf). However, the National Institutes of Health National Toxicology Program 

has not adopted IARC’s classification change and continues to classify formaldehyde as 

“reasonably anticipated to be a carcinogen in humans” 

(http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s089form.pdf).

 1 CDC added this reference on December 15, 2010 in response to an Information Request for Correction 

(http://aspe.hhs.gov/infoquality/request&response/35b8.pdf)
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 5

How to quantitatively relate measured air levels of formaldehyde to cancer risk is uncertain. 

Because many other factors play a role in the development of cancer and because formaldehyde 

is ubiquitous in the environment, no definitive level can be established that places humans in a 

“high-risk” category. The safest way to reduce risk for cancer is to limit exposure. Clinically 

useful biologic markers, such as blood or urine tests, also are lacking, further complicating the 

ability to link exposure with outcome. Because formaldehyde plays integral physiologic roles

and has a short half-life in the body, determining what is necessary for normal physiologic 

function and what is excessive and potentially harmful is difficult (Sullivan and Kreiger, 2001; 

Baselt, 1994). In general, the lower the level and shorter the duration of exposure, the lower the

risk for cancer and other health effects.

Regulations and Standards of Formaldehyde Levels

No federal regulation or standard exists for formaldehyde levels in residential settings. 

Occupational levels are not appropriate to apply to residential settings for a variety of reasons. 

For example, residential populations include children and elderly persons and thus are more 

diverse than occupational populations and possibly more susceptible to illness from exposure 

because of preexisting health conditions. Exposure times and circumstances in homes can vary 

substantially from those in occupational settings. Many occupational settings have ongoing 

monitoring programs and may have safety requirements to reduce formaldehyde exposure (US 

Department of Labor, 2007). Even for workers, regulations and standards established for 

formaldehyde by government agencies and other organizations—such as the Occupational Safety 

and Health Administration, CDC’s National Institute for Occupational Safety and Health, and the 

American Conference of Governmental Industrial Hygienists—differ markedly for both longand short-term exposures (Federal Register, 1992; NIOSH, 1992; ACGIH, 1993).

Various nonoccupational standards also vary The U.S. Department of Housing and Urban 

Development (HUD) regulates formaldehyde emissions from wood products used in the 

construction of manufactured housing. HUD’s maximum allowed levels for formaldehyde 

emissions from wood products are 200 ppb for plywood and 300 ppb for particle board 

(http://ecfr.gpoaccess.gov). The World Health Organization guideline for formaldehyde in 

nonoccupational settings is 100 ppb for 30 minutes. This guideline was developed to protect 

against sensory irritation in the general population, but it also represents an exposure level at 

which risk for upper respiratory tract cancer in humans is negligible (WHO, 1989). The State of 

California Office of Environmental Health Hazard Assessment (OEHHA) guideline for 

formaldehyde is less than typical ambient levels, it recommended an office level of 23 ppb

(http://www.oehha.ca.gov/air/chronic_rels/AllChrels.html).

OBJECTIVES

The objectives of this study were to

1. Determine formaldehyde levels in occupied trailers.

2. Determine factors or characteristics of occupied trailers—not specific to any particular 

type of trailer—that could affect formaldehyde levels.

3. Provide information to assist FEMA in making decisions about relocating residents from 

FEMA-supplied trailers still used in the Gulf Coast area.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 6

METHODS

To evaluate the formaldehyde levels and to determine potential factors and characteristics of 

occupied trailers that can impact formaldehyde levels, study investigators collected the following 

data for each participating trailer:

• A 1-hour, time-integrated indoor sample measurement of formaldehyde.

• A concurrent sample measurement of indoor temperature and RH

• A short questionnaire administered to adult residents to obtain demographic information 

about trailer residents and typical daily activities.

• A short walk-through survey to assess the indoor environment and the home exterior.

Study Personnel

Staff who collected the data were contractors from Bureau Veritas (Kennesaw, GA). Their 

training at the beginning of the study included review of recruitment, data collection, trailer 

visits, data records, and the protocol. CDC staff monitored contract staff throughout the study 

and were always available for consultation.

Trailer Selection

Using disproportionate stratified random sampling, CDC investigators selected 519 trailers for 

participation from a FEMA-provided list of 46,970 trailers in LA and MS that were identified as 

occupied as of November 2007. SAS 9.1 was used to randomly generate a list of sample trailers. 

The three trailer types most commonly used—travel trailer, park model, and mobile home—were 

divided into a total of 11 strata. Travel trailers comprised seven strata: the top six manufacturers 

(Gulfstream, Forest River, Fleetwood, Fleetwood CA, Pilgrim, and Keystone [which together 

represented 61% of occupied travel trailers]) and “all other” travel-trailer brands. Because 

Gulfstream was the most frequently used travel trailer, that brand was oversampled. Park models 

comprised two strata: the most common model manufactured by Silver Creek (21% of park 

models) and “all other” park model manufacturers. Mobile homes also comprised two strata: the 

most common model manufactured by Cavalier (17% of mobile homes used) and “all other”

manufacturers. Each brand in the “all other” groups made up <3% of the trailers.

The number of trailers selected was based on power calculations that allow researchers to draw 

statistically valid conclusions about the population of occupied trailers studied (i.e., FEMAsupplied trailers used) and for common trailer types and brands within that population of FEMAsupplied trailers. With a level of significance of 5% (95% confidence) and power of 80%, the 

goal was to sample a minimum of 38 trailers to detect an average difference of 30 ppb for each 

stratum. Sample sizes were calculated as tests for each stratum mean against the mean for the 

entire sample.

Within each stratum, each trailer was assigned a random number (e.g., SAS:

Randval=randuni[number]). Each list then was sorted in numeric order according to the random 

number assignment. In recruiting eligible households, investigators followed a specific protocol 

(Appendix A) and used these ordered active call lists to recruit participants for the study, 

beginning with number 1 and ending with number 120 for the Gulfstream stratum and with 
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 7

number 38 for each of the other 10 strata. When the occupant of a selected trailer could not be 

contacted, declined participation, or was ineligible, investigators called the next trailer on the list, 

adding trailers as necessary from a reserve list, until they had successfully enrolled 120 trailers in 

the Gulfstream stratum and 38 trailers in each of the other 11 strata.

Up to three telephone numbers were provided for each trailer. Over a 1-week period,

investigators attempted a total of 15 times separate attempts to contact a selected trailer. The 15 

attempts included various times of the day and days of the week. If unsuccessful after 15 

attempts, the trailer was moved to the “unable to contact” list and a new trailer from the reserve 

list was added to the active call list.

Contract staff followed a phone script (Appendix B) when speaking with the self-identified adult 

resident and recorded each attempt in a phone log (Appendix B). If the adult resident of an 

eligible household agreed to participate, a time was scheduled to conduct the sampling. If the 

adult resident declined to participate, the trailer was moved to the “refused to participate” list and 

a new trailer from the reserve list was added to the active call list.

Some enrolled households were expected to not complete the study for a variety of reasons. Each 

time it was determined that an enrolled trailer was to be removed from the list of participants, a 

new trailer from the reserve list was substituted and recruitment procedures as described above 

were followed. 

Eligibility Criteria

Adult residents who agreed to participate were enrolled in the study. Eligibility criteria for 

participation in the study specified that:

• The consenting adult resident was ≥ 18 years of age. 

• The adult resident resided in a FEMA-issued trailer in MS or LA at the time of phone 

recruitment.

• The adult resident reported that he or she spent at least 6 hours each day in a FEMAissued trailer.

• The adult resident agreed to participate.

Consent/Assent Process

Adult residents provided informed assent (Appendix C) which was first obtained from the 

contacted adult resident during the scripted recruitment phone call. A second informed consent 

form was provided to the participant and signed in person sample collection (Appendix D). All 

participants received appropriate notification of confidentiality. CDC’s Institutional Review 

Board reviewed and approved this study (CDC Protocol #5320, approved by CDC IRB-G on 

December 20, 2007).
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 8

Variables

The primary outcome variable was the 1-hour average level of formaldehyde measured in the air 

of occupied trailers. To determine potential factors of occupied trailers that can affect the 

measured formaldehyde levels, other variables were collected during an exposure assessment and 

walk-through.

Exposure Assessment Questionnaire

Investigators administered a short questionnaire (Appendix E) to the adult resident during the 1-

hour sample collection process. The questionnaire inquired about the demographics of the trailer 

occupants and the average number of hours spent inside and outside the trailer. It also inquired 

about factors that can influence the indoor environment of the trailer, such as occupant smoking 

and frequency of air conditioning, heating, and window use. Daily and recent activities in the 

trailer, such as cooking, also were recorded.

Environmental Walk-Through Survey

During the walk-through survey (Appendix E), investigators surveyed the interior and exterior of 

the trailer, observing such factors as holes and leaks, mold, type of cooking fuel, and working 

smoke detectors.

Formaldehyde Sample Collection

Investigators and FEMA field workers were present for each scheduled sampling appointment. 

Investigators collected a 1-hour sample of air in each participating trailer using the NIOSH 

Manual of Analytical Methods Method 2016 using Supelco S10 LpDNPH cartridges (St. Louis, 

MO) (http://www.cdc.gov/niosh/nmam/pdfs/2016.pdf). Staff also measured indoor temperature 

and RH. In an attempt to standardize living conditions between trailers, residents were asked to 

configure doors and windows as they would have them while they slept. No cooking or smoking 

was allowed in the travel trailers or mobile homes during the 1-hour sample collection period 

because these activities could affect formaldehyde levels.

Samples were collected using standard industrial hygiene pumps. Samples were drawn at a flow 

rate of 500±50 mL per minute for 1 hour at a height of 4 feet, which is comparable to a person’s 

breathing zone while sitting. An investigator observed sample collection at all times. 

Investigators followed all quality assurance and quality control standards as outlined in the 

standard operating procedures for field collection (Appendix F).

Samples were analyzed for formaldehyde levels at the Bureau Veritas laboratory in Novi, 

Michigan. The Bureau Veritas laboratory is a contract laboratory for NIOSH and follows NIOSH 

data quality objectives in its sampling and analysis.

Temperature and Relative Humidity Sample Collection

A concurrent 1-hour reading of temperature and RH was collected in the center of the trailer 

primary living room using a HOBO® temperature and RH logging instrument manufactured by 

Onset Computer Corporation (Bourne, MA). The instrument collected data at 5-minute intervals. 

Data were collected for a minimum of 70 minutes, beginning at least 5 minutes before and 

lasting at least 5 minutes after collection of the formaldehyde sample at each trailer.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 9

Sample Collection Data Sheet

Investigators completed a data sheet (Appendix G) for formaldehyde, temperature, and RH. 

Information included sample start and finish time, location of sample collection, and flow 

calibration results before and after sample collection was recorded. The data sheet accompanied 

the questionnaire and the walk-through survey (Appendix E).

Data Collection, Entry, Editing, and Management

Investigators collected all questionnaire, survey, and field data; labeled all samples and 

documentation with a unique alphanumeric identifier; and logged all paperwork and samples as 

they completed each trailer. Strict quality assurance and quality control procedures were 

observed.

Investigators entered all field data into an electronic database. All participant information 

remained confidential and was used only for the study. Access to data was restricted to those 

involved in conducting the study. In addition, all reports—published and internal—were based 

only on aggregate data. Investigators returned or destroyed all data sources after delivering the 

final approved database to CDC.

Statistical Analysis

All statistical analyses were conducted using SAS 9.1. The SURVEYMEANS, SURVEYREG, 

and SURVEYFREQ procedures were used to account for the stratified sampling design. 

Unweighted frequencies of questionnaire items were calculated using the FREQ procedure.

Data were examined and potential misclassifications of trailers resolved. The manufacturer, 

manufacturer’s vehicle identification number, and trailer type were examined to confirm the 

categorization of each trailer. In cases where a trailer was recategorized, two independent 

evaluators agreed on the new classification. 

A natural log transformation was applied to the formaldehyde levels to normalize the 

distribution. Tests for normality were conducted on the transformed levels, and the levels were 

plotted to examine the form of the distribution. Univariate linear regression models were 

constructed to evaluate the significance of selected questionnaire items in predicting the natural 

log of formaldehyde levels. Variables with cell counts of five or fewer were not included in the 

regression models.

Temperature and RH were evaluated separately as both continuous and categorical variables. 

Recorded signs of mold in the living area of the trailer were used to create a dichotomous 

variable indicating whether the trailer had <1 ft2 of mold versus >1 ft2 of mold.

Because the SAS SURVEYREG procedure does not include an option for automated model 

selection, CDC staff manually performed a backward elimination procedure. All independent 

variables with cell counts greater than five initially were entered into the linear regression model. 

At each step, the variable contributing the least to the model, as assessed by the F statistic, was 

removed. The final model included variables that were significant at a P of <0.05.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 10

RESULTS

Participation Rates

During recruitment, investigators contacted residents at 1137 (76%) of the 1489 trailers on the

FEMA-supplied list (Figure 1). Of the 717 eligible trailers, occupants in 519 (72%) participated. 

Reasons for ineligibility of the remaining 420 trailers included trailer not occupied (367 [87%]);

trailer type no longer needed for its stratum (27 [6%]); trailer occupant unable to schedule an 

appointment time because of work, travel, hospitalization, or other reasons (15 [4%]); hostility 

by occupants (3 [1%]); and unknown reasons (8 [2%]).

Most trailers sampled were in LA and were located on private land (Table 1). Most were issued 

in 2005 and therefore were at least 2 years old at the time of testing. Seventy-seven percent of 

total occupants were adults. Recategorization of trailers resulted in reclassification of 35 trailers 

(7%) to new strata. The majority of these reclassified trailers came from the nonspecific “other” 

strata.

Overall Range and Variability of Formaldehyde Levels

The geometric mean (GM) formaldehyde level for all trailers sampled was 77 ppb (95% 

confidence interval [CI]: 70–85; range: 3–590 ppb). Throughout this report, when mean 

formaldehyde levels are discussed they will refer to GM formaldehyde levels. The GM

formaldehyde level was 81 ppb for travel trailers (95% CI: 72–92), 44 ppb for park models (95% 

CI: 38–53) and 57 ppb for mobile homes (95% CI: 49–65) (Figure 2). GM formaldehyde levels 

varied significantly among travel trailers, park models, and mobile homes (P < 0.001) and 

ranged widely in all types of trailers. In all three trailer types, some trailers had formaldehyde 

levels ≥ 100 ppb. Mobile homes and travel trailers each had levels ≥ 300 ppb (Table 2). GM

formaldehyde levels differed significantly among strata, but each stratum included some trailers 

with levels ≥ 100 ppb (Table 3).

Occupant Activities

The investigation included occupant activities in the trailers (Table 4). Air conditioning was used 

<4 hours per day in 71%; heat was used <4 hours a day in 56%; and space heaters were used in 

44%. For 34% of trailers, residents reported someone had smoked in the trailer within 2 weeks 

before the sampling. Eighty-one percent of respondents cooked in their trailers. Pets were present 

in 25% of trailers, with dogs (20%) most commonly reported. More than 80% of respondents 

spent >8 hours in their trailer each day.

Occupant activities directly preceding the sampling period were recorded to determine whether 

they significantly affected sampling results. Within 3 hours before testing, 44% of homes had 

windows, doors, and scuttles open, and smoking had occurred in 19%. Other activities in the 

week before testing included use of air fresheners (61%); candles (24%); and glue, paint, or 

furniture finish (3%). These finding did not correlate with any specific type of trailer.

Trailer Characteristics

Specific characteristics of each sampled trailer were recorded. Respondents reported roof leaks 

in 17% of trailers, pipe leaks in 15%, and mold in 21%.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 11

Walk-Through Survey

On the day of sampling, investigators walked through each trailer to record specific 

characteristics and information (Table 5). Propane gas was the most commonly used fuel for 

cooking (71% of trailers). Six percent of trailers had at least 1 ft2 of mold. Twenty-nine percent 

of trailers did not have a functioning smoke detector.

Multivariate Analysis

Backward elimination modeling yielded a final regression model containing the following 

statistically significant variables: stratum (P < 0.0001); average temperature in degrees F (P <

0.0001); RH expressed as a percentage (P < 0.0001); a dichotomous variable indicating whether 

doors, windows, or scuttles were open in the 3 hours before testing (P = 0.02); and a 

dichotomous variable indicating the amount of mold observed in the trailer (≥ 1 ft2) (P = 0.05). 

The dependent variable was the natural log of the formaldehyde levels. Temperature accounted 

for the most variation in the natural log of formaldehyde levels explained by the model (Figures 

3 and 4) show the unadjusted relationship between the natural log of formaldehyde and 

temperature and humidity, respectively. Temperature ranged from 41oF to 91oF, and RH was 

23%–88%.

Temperature and RH were evaluated separately as both continuous and categorical variables. 

Results were similar, so investigators included the continuous variables in the final model. 

Interactions between independent variables were not significant.

The presence of >1 ft2 of mold was associated with a significant increase in GM formaldehyde 

levels (adjusted mean 86 ppb versus 63 ppb) (Table 6). Windows, doors, or scuttles open in the 3 

hours before testing was associated with a significant decrease in GM formaldehyde levels 

(adjusted mean 65 ppb versus 83 ppb) (Table 7). Although each of three strata (Forest River, 

other park models, and other mobile homes) contained fewer than 38 trailers, contrasts 

comparing the GM formaldehyde level in each of them to the overall GM of the others still 

showed significant differences (P = 0.01, 0.01, and 0.04, respectively).

GM formaldehyde levels in travel trailers manufactured by Fleetwood and Fleetwood CA were 

significantly lower than levels in the other travel trailers combined, after adjustment for 

covariates (P < 0.001 for both). They did not differ significantly from each other. GM

formaldehyde levels for Pilgrim, Keystone, and Gulfstream were significantly higher than for the 

other travel trailers combined, after adjustment for covariates (P<0.001 for all three). They did 

not differ significantly from each other. After adjustment for covariates, levels in Silver Creek 

park models were significantly lower than those in other park models (P = 0.004), and levels in 

Cavalier mobile homes were significantly higher than those in other mobile homes (P = 0.006).

Table 8 presents the adjusted GM formaldehyde level by stratum from the multivariate model.

The parameter estimates (Table 9) can be used to calculate predicted formaldehyde levels. 

However, extrapolating beyond observed levels is not recommended. As an example, a Keystone 

travel trailer with an average temperature of 65oF; an average RH of 45%; no open doors, 

windows, or scuttles in the 3 hours before testing; and mold (≥ 1 ft2

) would have a predicted 

formaldehyde level of 88.5 ppb:
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 12

Natural log of formaldehyde = 0.012 + 0.096 + 65(0.052) + 45(0.017) +0(-0.243) + 0.311

Predicted formaldehyde: 88.5 ppb

DISCUSSION

Formaldehyde levels in the trailers in this study were higher than average levels in U.S. mobile 

homes and traditional homes reported in recent studies (Weisel et al., 2005; Gordon et al., 1999). 

As the formaldehyde level rises, risk for health consequences presumably also rises. At higher 

levels, people can have acute symptoms, such as coughing and irritated eyes, nose, throat, and 

upper respiratory system. Even at levels too low to cause such symptoms, risk for cancer can 

increase. No specific level of formaldehyde separates "safe" from "dangerous,” especially in 

regard to cancer.

In this study, certain human activities were associated with higher formaldehyde levels. Open

windows, doors, or scuttles decreased formaldehyde levels, indicating ventilation of trailers is an 

important recommendation to occupants. Keeping windows, doors, or scuttles open and the using

air conditioning were associated with decreased levels of formaldehyde in trailers in a previous 

study (ATSDR, 2007). Yet many trailer air conditioners recirculate air and do not provide 

outside ventilation. Thus, less use of air conditioning may indicate increased ventilation because 

doors, windows, and scuttles are more likely to be open. Results of this study show a low use of 

air conditioning during the study period. Most trailers had working air conditioning, but most 

people did not use it more than 4 hours each day, most likely because the study was conducted 

during the winter; other factors could include cost and noise.

Smoking by occupants, though not significantly associated with increased formaldehyde levels in 

the multivariate analysis, was common and remains an important issue because cigarettes are a 

source of formaldehyde. Cigarette smoke also contains a wide range of other toxic and irritating 

compounds associated with increased health risk that can worsen air quality in the trailers.

The presence of mold (≥ 1 ft2

) (6% of trailers) was associated with higher formaldehyde levels. 

Mold also can contribute to decreased indoor air quality and cause respiratory symptoms.

Cooking, particularly without outdoor-venting range hoods, can affect formaldehyde levels. The 

unvented combustion from gas-fired stoves can be a source of formaldehyde and other air 

pollutants and can increase the temperature and RH inside the trailer.

Increased indoor temperature and RH were associated with increased formaldehyde levels. These 

associations indicate exposure risks could increase during the summer, perhaps dramatically, 

with warmer and more humid weather. Formaldehyde levels during the winter may not represent 

summer levels.

Stratification was conducted to assess the possibility of an elevated formaldehyde level in one 

brand or a group of brands. Some brands showed higher GM formaldehyde levels than others, 

although this study showed all brands with some trailers ≥ 100 ppb, levels at which health effects 

have been described in sensitive persons. Formaldehyde levels varied by trailer type, but all 
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 13

types tested had some levels ≥ 100 ppb (Ritchie et al., 1987; Main et al., 1983; Bender et al., 

1983).

LIMITATIONS

Study results are not representative of trailers purchased and used in other places and other 

situations because the sample for this study was selected only from occupied FEMA-supplied 

trailers in LA and MS. Formaldehyde levels in other trailers used elsewhere could differ by age, 

characteristics of manufacture, circumstances of use, or characteristics of environment.

Formaldehyde levels are expected to be lower in cooler temperatures and lower RH because of 

the processes of formaldehyde off-gassing. Therefore, levels measured in this study are likely to 

underestimate past levels—when trailers were hotter and more humid—and future levels—

during summer months. Many of these trailers were >2 years old, and previous studies have 

shown highest formaldehyde levels in newer trailers and homes (Hodgson et al., 2000; Gordon et 

al., 1999), so residents were probably exposed to higher levels of formaldehyde when their 

trailers were newer.

Formaldehyde was measured at a central location in the trailer, and different locations in the 

trailer could have different formaldehyde levels. However, as a gas, formaldehyde is likely to 

diffuse evenly throughout the trailer. The results of this study do not apply to trailers used in 

other places and situations because this representative sample was selected only from FEMAsupplied trailers in LA and MS. This study does not assess the health status of people currently 

living in FEMA trailers, but further studies are planned to investigate potential health effects 

from living in trailers.

CONCLUSIONS

1. In many trailers tested, formaldehyde levels were higher than typical U.S. indoor levels.

2. The average level of formaldehyde in all trailers was 77 ppb, and many trailers had 

higher levels (range: 3 ppb–590 ppb) . These are higher than U.S. background levels, and 

occupant health could be affected at the levels recorded in many trailers.

3. These measured levels probably underrepresent occupant exposures in the early months 

of occupation and even the average exposure over time the trailers were occupied 

because formaldehyde levels tend to be higher in newly constructed trailers and during 

warm weather.

4. Higher indoor temperatures and RH were associated with higher formaldehyde levels in 

this study, independent of trailer type or brand.

5. Formaldehyde levels varied by trailer type, but all types tested had some levels ≥ 100 

ppb, at which acute health effects can occur in sensitive persons.

6. Travel trailers had significantly higher average formaldehyde levels than park models or 

mobile homes. Travel trailers also had higher proportions of trailers with formaldehyde 

levels ≥ 100 and ≥ 300 ppb than park models or mobile homes.

7. Because some types and brands had lower average formaldehyde levels, trailers might be 

able to be manufactured or used in ways that reduce levels. Additional studies are under

way to address this possibility.

8. Factors such as temperature; RH; closed windows, doors, and scuttles; and presence of 
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 14

mold (≥ 1 ft2) were associated with increased formaldehyde levels in the trailers. These 

were not assessed with respect to any specific type of trailer.

9. Only 71% of trailers sampled had a working smoke detector. Education is needed about 

the need for smoke detectors in the trailers and testing to ensure they function correctly.

RECOMMENDATIONS

Recommendations for Public Health, Emergency Response, and Housing Officials

1. These conclusions support decisions made need to relocate residents of the U.S. Gulf 

Coast region displaced by hurricanes Katrina and Rita who still live in trailers move 

quickly before temperatures in the region increased. On the basis of observations and 

previous scientific literature, priority should be given as follows:

a. Persons currently experiencing symptoms possibly attributable to formaldehyde 

exposure,

b. Especially vulnerable persons (e.g., children, the elderly, and those with chronic 

diseases), and

c. Persons living in trailer types that tend to have higher formaldehyde levels.

2. Follow-up will require collaboration among multiple agencies—including FEMA, HUD, 

CDC, and state and local officials—to achieve safe, healthy housing for people displaced 

by hurricanes Katrina and Rita who continue to live in FEMA-supplied trailers.

3. Follow-up will require multiagency collaboration involving HUD, CDC, and others to 

assess the potential for formaldehyde levels in trailers used in other places and contexts, 

including trailers used for recreation, permanent housing, schools, and offices.

4. Federal, state, and local officials should consider how best to provide necessary 

assistance to the Louisiana and Mississippi state health departments to ensure adequate 

follow-up, including medical needs, for residents with health and medical concerns 

resulting from formaldehyde exposure while residing in FEMA-provided travel trailers, 

park models, and mobile homes. 

5. Federal, state, and local officials should consider supporting establishment of a registry of 

people who resided in FEMA-supplied trailers in the U.S. Gulf Coast region.

Recommendations for Residents Awaiting Relocation

1. Spend as much time as possible outdoors in fresh air.

2. Open windows, doors, and scuttles as often as possible to let in fresh air.

3. Try to maintain the temperature inside trailers at the lowest comfortable level.

4. Do not smoke, especially not inside. 

5. If you have health concerns, see a doctor or another medical professional.

6. All of these recommendations apply particularly to families with children, elderly

persons, and those with chronic diseases, such as asthma.

Further CDC Action

1. CDC notified participants about their study results by personal visits from members of 

the U.S. Public Health Service Commissioned Corps and FEMA representatives and by 

hand-delivered letters.

2. At a series of 14 public availability sessions in LA and MS, CDC staff were available to 

talk with concerned and interested persons, provide information, and answer questions.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 15

3. CDC is assessing formaldehyde levels across different models and types of unoccupied 

trailers to identify factors that decrease or increase those levels. This assessment also 

involves identifying cost-effective ways to reduce formaldehyde levels in trailers.

4. CDC is developing a protocol for a long-term health study, with a respiratory focus, of 

children who resided in FEMA trailers and mobile homes in LA and MS.

5. CDC provided educational materials and information to trailer residents about their risk 

for exposure to formaldehyde and ways to improve indoor air quality and health.

6. CDC reconvened a panel of experts on this issue to identify and provide input on health 

issues potentially associated with long-term residence in trailers.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 16

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http://aspe.hhs.gov/infoquality/request&response/35b8.pdf
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 20

Figure 1. Recruitment of Participants in a Study of Occupied FEMA-Supplied Trailers in 

Louisiana and Mississippi, December 2007–January 2008

Contact Attempted 

in 1489 Trailers

352 (24%)

Trailers Excluded: 

Wrong # or 

Disconnected Phone 

1137 (76%)

Trailers Contacted

420 (37%)

Trailers Ineligible

717 (63%)

Trailers Eligible

101 (14%)

Refused 

Participation

by Phone

616 (86%)

Agreed to

Participate

97 (16%)

Refused at Time

of Sampling

519 (84%)

Accepted and Tested

Cooperation Rate: 

 519/717 = 72%
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 21

Figure 2. Geometric Mean Formaldehyde Levels in Occupied FEMA-Supplied Trailers, 

Louisiana and Mississippi, December 2007–January 2008 

GM = geometric mean; ppb = parts per billion (divide by 1000 to get parts per million); CL = confidence limit. 

0

10

20

30

40

50

60

70

80

90

100

Formaldehyde (ppb)

All Occupied

Trailers

Travel Trailers Mobile Homes Park Models

− Upper 95% CL − Lower 95% CL Geometric Mean
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 22

Figure 3. Association of Indoor Temperature with Natural Log Formaldehyde Levels in 

Occupied FEMA-supplied Trailers in Louisiana and Mississippi, December 2007–

January 2008 

 Range: 41oF–91oF 

0

1

2

3

4

5

6

7

40 50 60 70 80 90 100

Temperature (oF)

Ln Formaldehyde Levels
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 23

Figure 4. Association of Indoor Relative Humidity with Natural Log Formaldehyde Levels 

in Occupied FEMA-supplied Trailers in Louisiana and Mississippi, December 

2007–January 2008 

 Range: 23%–88% relative humidity. 

0

1

2

3

4

5

6

7

20 30 40 50 60 70 80 90

Relative Humidity (%)

Ln Formaldehyde Levels
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 24

Table 1. Demographics of Trailers and Occupants in 519 Occupied FEMA-Supplied 

Trailers in Louisiana and Mississippi, December 2007–January 2008

Category Variable No. (%) Weighted 

(%)

State Louisiana 408 79 80

Mississippi 111 21 20

Trailer 

locations

Private land 374 72 77

Public land 127 24 20

Unknown/Undetermined 18 3 3

Year trailer

was

manufactured

2005 258 50 --

2006 128 25 --

Unknown 133 26 --

Residents -- --

No. adult residents 

(age >18 years)

852 77 --

No. teen residents 

(age 13 ≤ 17 years)

97 9 --

No. child residents 

(age 3 ≤ 12 years)

120 11 --

No. baby residents 

(age <2 years)

41 4 --

Average no. residents 

per trailer

2 -- --

Utilities Paid by occupant 420 81 83

Paid by FEMA 90 17 16

Paid by other 9 2 1
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 25

Table 2. Formaldehyde Levels in 519 Occupied FEMA-Supplied Trailers in Louisiana and Mississippi, 

December 2007–January 2008

GM = Geometric mean; ppb = parts per billion (divide by 1000 to get parts per million); CI = confidence interval.

Trailer 

Type

No. Formaldehyde

GM (ppb)

Range 

(ppb)

95% CI

for GM (ppb)

Weighted Percentage

of the Sample with Levels 

≥ 100 ppb ≥ 300 ppb

Travel 

trailer

360 81 3–590 72–92 42% 5%

Park 

model

90 44 3–170 38–53 14% 0%

Mobile 

home

69 57 11–320 49–65 9% <1%
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 26

Table 3. Formaldehyde Levels by Manufacturer in 519 Occupied FEMA-Supplied Trailers in Louisiana and Mississippi, 

December 2007–January 2008

GM = geometric mean; ppb = parts per billion (divide by 1000 to get parts per million); CI = confidence interval.

Home Type Brand No. in 

stratum

No. in 

sample

Formaldehyde

GM (ppb)

Range 

(ppb)

95% CI

for GM (ppb)

Weighted Percentage

of the Sample with Levels 

≥ 100 ppb ≥ 300 ppb

Travel 

trailer

Gulfstream 14,624 123 104 3–590 88–123 56% 9%

Forest River 3,220 36 82 17–510 61–109 42% 6%

Fleetwood 2,371 47 39 3–140 32–48 6% 0%

Fleetwood CA 1,699 39 43 7–300 34–55 13% 3%

Pilgrim 1,584 39 108 25–520 85–136 51% 3%

Keystone 1,395 38 102 23–480 79–131 53% 11%

Other 15,637 38 74 11–330 57–96 37% 3%

Park model Silver Creek 224 53 33 3–170 29–39 6% 0%

Other 809 37 48 11–160 39–60 16% 0%

Mobile 

home

Cavalier 921 42 78 14–320 65–95 36% 2%

Other 4,486 27 53 11–120 45–63 4% 0%

Total 46,970 519 77 3–590 70–85 38% 5%
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 27

Table 4. Activities Reported by Occupants in 519 Occupied FEMA-Supplied 

Trailers in Louisiana and Mississippi, December 2007–January 2008

Category Variable No. (%) Weighted (%)

Temperature and 

ventilation

No. hours air conditioning used 

per day in week before testing

 <1 hour 212 41 44

 1–4 hours 136 26 27

 5–8 hours 56 11 10

 >8 hours 82 16 13

 Don’t know 33 6 6

No. hours heat used per day in 2 

weeks before testing

 <1 hour 134 26 28

 1–4 hours 154 30 29

 5–8 hours 98 19 21

 >8 hours 106 20 16

 Don’t know 27 5 6

Space heaters regularly used

 Yes 198 38 44

 No 301 58 53

 Don’t know 20 4 2

Windows/doors/scuttles left open 

within 3 hours before testing

 Yes 202 39 44

 No 299 58 54

 Don’t know 18 3 2

Time windows/doors/scuttles left 

open before testing

 <1 hour 171 33 37

 1–4 hours 75 14 14

 5–8 hours 9 2 2

 >8 hours 41 8 10

 Don’t know 223 43 37

Smoking No. people who have smoked in 

trailer the prior 2 weeks

 None 335 65 66

 1 112 22 21

 >2 72 14 13

Someone smoked in the 3 hours 

before testing

 Yes 105 20 19

 No 399 77 79

 Don’t know 15 3 2

Cooking Anyone cook in trailer
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 28

 Yes 410 79 81

 No 82 16 15

 Don’t know 27 5 4

Anyone cook in trailer in the 3 

hours before testing:

 Yes 86 17 14

 No 397 76 80

 Don’t know 11 2 2

 Question skipped 25 5 5

Time indoors Average amount of time per day 

respondent spent inside trailer

 <1 hour 0 0 0

 1–4 hours 9 2 1

 5–8 hours 70 13 14

 >8 hours 424 82 82

 Don’t know 16 3 3

Household member sleeps in 

trailer

 Yes 482 93 93

 No 13 3 3

 Don’t know 24 5 4

Pets No. trailers with at least 1 dog 113 22 20

No. trailers with at least 1 cat 30 6 5

No. trailers with at least 1 bird 10 2 1

No. trailers with other pets 11 2 1

Products used Pesticides sprayed in past month:

 Yes 86 17 17

 No 410 79 79

 Don’t know 23 4 4

Candles used in the week before

testing

 Yes 128 25 24

 No 391 75 76

Air freshener used in week 

before testing

 Yes 308 59 61

 No 211 41 39

Glue, paint, or furniture finish 

used in week before testing

 Yes 17 3 3

 No 502 97 97

Mothballs used in week before

testing

 Yes 5 1 1

 No 514 99 99
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 29

Closet Fresh used in week before

testing

 Yes 5 1 1

 No 514 99 99

Nail polish used in week before 

testing

 Yes 53 10 9

 No 466 90 91

Trailer condition Roof leaked in the past 3 months

 Yes 72 14 17

 No 412 79 77

 Don’t know 35 7 6

Pipe leaked in past 3 months

 Yes 70 13 15

 No 427 82 81

 Don’t know 22 4 4

Reported mold in past 3 months

 Yes 93 18 21

 No 403 78 75

 Don’t know 23 4 3
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 30

Table 5. Walk-Through Observations by Investigators in 519 Occupied FEMASupplied Trailers in Louisiana and Mississippi, December 2007–January 2008

Category Variable No. (%) Weighted 

(%)

Trailer characteristics Problems seen with the roof

 Yes 33 6 6

 No 483 93 93

 Don’t know 3 1 <1

Signs that water spills onto siding

 Yes 66 13 13

 No 453 87 87

Signs of mold in living area of

trailer

 Yes, <1 ft2 26 5 4

 Yes, 1–4 ft2 17 3 4

 Yes, >4 ft2 11 2 2

 No 465 90 90

Carpeting in trailer

 Yes 191 37 43

 No 328 63 57

Air conditioning Forced air

 Yes 273 53 40

 No 246 47 60

Rooftop air conditioning

 Yes 224 43 57

 No 295 57 43

No working air conditioning

 Yes 3 1 <1

 No 516 99 99

Other type of air conditioning

 Yes 7 1 <1

 No 512 99 99

Heating Central heating/forced air

 Yes 463 89 89

 No 56 11 11

Space heater

 Yes 91 18 21

 No 428 82 79

No working heating system

 Yes 2 <1 1

 No 517 99 99

Other type of heating system

 Yes 16 3 2

 No 503 97 98
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 31

Fuel source for 

cooking

Electricity

 Yes 214 41 23

 No 305 59 77

Propane gas

 Yes 272 52 71

 No 247 48 29

Natural gas

 Yes 3 1 <1

 No 516 99 99

Charcoal or wood

 Yes 0 0 0

 No 519 100 100

Other

 Yes 7 1 2

 No 512 99 98

Smoke detectors Functioning smoke detectors

 Yes 390 75 71

 No 129 25 29
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 32

Table 6. Adjusted Geometric Mean Formaldehyde Level from Occupied FEMASupplied Trailers in Louisiana and Mississippi that Had Mold (≥ 1 ft2

), December 

2007–January 2008, from Multivariate Analysis

Mold > 1 ft2 No. Trailers Adjusted GM

Formaldehyde 

(ppb)*

Yes 28 86

No 491 63

*Adjusted for stratum, average temperature, relative humidity, and open 

windows/doors/scuttles 3 hours before testing (all significant multivariate variables). 

GM=geometric mean.

Table 7. Adjusted Geometric Mean Formaldehyde Level from Occupied FEMASupplied Trailers in Louisiana and Mississippi that Had Open Windows, Doors, or 

Scuttles 3 Hours Before Testing, December 2007–January 2008, from Multivariate 

Model

Windows/Doors/

Scuttles Open

No. Trailers Adjusted GM

Formaldehyde 

(ppb)*

Yes 202 65

No 299 83

*Adjusted for stratum, average temperature, relative humidity, and presence of mold (≥ 1 

ft2

) (all significant multivariate variables). GM=geometric mean.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 33

Table 8. Adjusted Geometric Mean Formaldehyde Level from Occupied FEMASupplied Trailers in Louisiana and Mississippi, by Stratum, December 2007–

January 2008, from Multivariate Model

*Adjusted for average temperature, relative humidity, windows/doors/scuttles open 3 

hours before testing, and presence of mold (≥ 1 ft2

) (all significant multivariate 

variables). GM = geometric mean.

Stratum Adjusted GM Formaldehyde Level 

(ppb)*

Travel trailer

 Gulfstream 111

 Pilgrim 129 

 Fleetwood CA 44

 Fleetwood 42

 Forest River 102

 Keystone 122

 Other 90

Park model

 Silver Creek 37

 Other 55

Mobile home

 Cavalier 84

 Other 62
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 34

Table 9. Estimated Regression Coefficients for Modeling of Statistically Significant 

Variables of Occupied FEMA-Supplied Trailers in Louisiana and Mississippi, 

December 2007–January 2008 

Variable Estimate P value

Intercept 0.012 (α) 0.983

 Gulfstream travel trailer Reference group

 Pilgrim 0.148 (ß 1) 0.232

 Fleetwood CA - 0.917 (ß 2) <0.001

 Fleetwood - 0.965 (ß 3) <0.001

 Forest River - 0.085 (ß 4) 0.600

 Keystone 0.096 (ß 5) 0.477

 Other travel trailer - 0.215 (ß 6) 0.114

 Silver Creek park model - 1.094 (ß 7) <0.001

 Other park model - 0.695 (ß 8) <0.001

 Cavalier mobile home -0.275 (ß 9) 0.016

 Other mobile home - 0.583 (ß 10) <0.001

Temperature (°F) 0.052 (ß 11) <0.001

Relative humidity (%) 0.017 (ß 12) <0.001

Windows/doors/scuttles

open (yes)

- 0.243 (ß 13) 0.017

Mold (≥ 1 ft2) 0.311 (ß 14) 0.052

 y = natural log of formaldehyde levels (ppb).

Formaldehyde Level Multivariate Model:

y = 0.012 + 0.148x1 - 0.917x2 - 0.965x3 - 0.085x4 + 0.096x5 - 0.215x6 - 1.094x7 - 0.695x8

- 0.275x9 - 0.583x10 + 0.052x11 + 0.017x12 - 0.243x13 + 0.311x14
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 35

APPENDIX A:

PROTOCOL FOR TRAILER SELECTION AND RECRUITMENT

CONTACTING PARTICIPANTS: Materials needed 

1. You will receive a stratified list of names and up to 3 phone numbers of residents 

in trailers from a CDC representative. This list represents the people whom you 

will contact for participation in the study.

2. For each trailer, you will need one clean phone log form (Appendix B) to log all 

attempted and successful calls.

3. You will need a copy of the telephone script (Appendix B) to ensure that each 

conversation is consistent.

4. You will need a clean copy of the “Obtaining Assent” form (Appendix C) for 

each trailer contacted.

CONTACTING PARTICIPANTS: Conducting the phone calls 

1. You will need to make the calls from the provided spreadsheet. 

2. Begin with the first name on the list and call them using the first number 

provided. 

3. If you are unable to get an answer, try the next phone number provided. 

4. After each attempt, record the information in the phone log (Appendix B).

5. Fifteen attempts using each provided number must be made before ending the 

recruitment of the person from the contact list. Over half of these attempts 

should be made after 5 pm in the event that the contacts are not at home to 

receive the call during the day. 

6. If you are unable to contact a trailer after making fifteen attempts for each

provided phone number, the majority of which attempted after 5 pm, file the 

recorded phone log into a folder labeled “Unable to Contact”.

If you are unable to reach a contact:

If you are able to contact a person in the trailer

7. When someone answers the phone, use the phone script (Appendix B) to guide 

the conversation.

:

8. If the adult resident is not available, you will need to continue efforts to make 

contact with him/her. 

9. If the adult resident is NOT interested in participating, note refusal in the phone 

log. File the phone log into a folder labeled “Refused”.

10. If the adult resident is interested in participating, ensure that they are eligible 

using the criteria outlined in the phone script.

11. If the adult resident agrees to participate, obtain verbal assent (Appendix C) and 

set up an appointment date and time with the adult resident.

12. Record “Agreed” in the phone log and file the phone log AND assent form in a 

folder labeled “Agreed”. 
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 36

RECRUITMENT COMPLETION

1. Recruitment is complete when all 11 strata have been completed. This will 

consist of at least 500 trailers total. 

PARTICIPANT FOLLOW-UP: Appointment reminder

1. Prior to their appointment, call the adult resident to confirm the sampling date 

and time

2. If the respondent can no longer make the appointment, reschedule the 

appointment.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 37

APPENDIX B:

PHONE LOG FOR PARTICIPANT RECRUITMENT

Interviewer initials _______

Number on spreadsheet _______________________________________

Trailer VIN _______________________________________

Address _______________________________________ 

Adult resident name _______________________________________

Phone number (s) 1:______________________________

2:______________________________

3:______________________________

Interviewer must make at least 15 attempts for each provided phone number (of 

which, half of the attempts must be conducted in the evening, after 5 pm) to contact each 

potential trailer.

Date called

(mm/dd/yy)

Time 

called

(am/pm)

Phone 

number 

called 

(1, 2, or 3)

I=For initial 

contact

F=Follow-up call

A=Name of 

alternative adult 

resident 

representative 

Status

(No answer,

Left message, 

Call back, 

Agreed, 

Refused, 

Excluded)

Recommended

call back time

(am/pm)
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 38

APPENDIX B, con’t:

TELEPHONE SCRIPT FOR PARTICIPANT RECRUITMENT

IF CHILD ANSWERS THE PHONE:

Hi, may I speak with your mother or father please? 

IF NO ADULT IS HOME:

Okay. Could you please tell me what would be a good time to call back?

[NOTE IN PHONE LOG]

Thank you, I’ll try calling back later.

IF AN ADULT ANSWERS THE PHONE:

Hello, this is ____________ calling for the Centers for Disease Control and Prevention. 

Is this the ___ (NAME)______residence? I am working with FEMA and the 

Louisiana and Mississippi Departments of Public Health to find out if there is 

formaldehyde (a potentially harmful chemical) in the trailers in which people are living. 

We have picked some trailers at random, like flipping a coin. May I ask if you are an 

adult resident living in a FEMA-owned trailer? 

IF NO

Okay, we will be working with all adult residents who are 18 years or 

older. What is a good time to call back to speak with him or her? And is 

this the best number to reach him/her? 

,

[NOTE NAME AND TIME IN PHONE LOG]

Thank you, I’ll try calling back later.

IF YES

We are asking the people who live in the trailers to let us test the indoor 

air for formaldehyde. We have picked your trailer as one that we would 

like to test. 

,

What we learn will help the federal government make decisions about if 

some people need to be moved out of their trailers to protect their health. 

For your inconvenience, a $50 gift card will be given to you at the 

completion of the study. Participation is voluntary. Do you think you 

may be interested in participating?

IF NO

Thank you. I appreciate you taking time out to talk. 

IF YES
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 39

Great. I would like to first ask you a few questions about yourself 

and your trailer. GO TO CRITERIA (below)

CRITERIA 

1. Are you, as an adult resident, 18 years in age or older?

 If YES, continue to question 2

 If NO, go to “End of interview for exclusions” 

2. Do you still live in a FEMA-issued trailer more than 6 hours per day? 

 If YES, continue to next section

 If NO, go to “End of interview for exclusions” 

IF YES is answered for questions 1-2:

If you agree to have us test your trailer, several things will take place:

1. We will set up a time to visit your trailer soon. The visit will not 

take more than an hour and a half. Cooking and smoking will not 

be allowed during the testing process.

2. We will ask you some questions about how you cook in your home 

and if people smoke in your home.

3. We will look around your home and fill out a short form about 

what type of heating you have, what type of stove you cook on, 

what type of air conditioner you have, and other similar questions.

4. We will test your trailer for formaldehyde and will also measure 

the temperature and humidity. We will deliver the test results of 

your trailer to you about a month after we test it. 

5. For your time and inconvenience, you will also receive a $50 gift 

card

Are you interested in participating in this study? 

IF YES

GO TO “WHEN SOMEONE AGREES TO PARTICIPATE” 

IF NO

Okay, thank you so much for your time. 

[HANG UP AND RECORD IN PHONE LOG AS REFUSAL]

END OF INTERVIEW FOR EXCLUSIONS

Thank you very much for your interest and for your willingness to be in the study. 

Unfortunately, it is important that people in our study be the adult resident and are 18 

years or older. Also, because we are interested in the formaldehyde levels that people are 

currently exposed to, we are working with those who are still living in their FEMAissued trailer. Thank you again for your time. [RECORD AS EXCLUSION IN PHONE 

LOG]
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 40

WHEN SOMEONE AGREES TO PARTICIPATE

Go to Appendix C: OBTAINING ASSENT [RECORD AS AGREED IN PHONE LOG]
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 41

APPENDIX C:

OBTAINING ASSENT

Thank you for helping us with this important project. Everything you tell us and all your 

test results will be kept private to the extent allowed by the law. To protect your privacy, 

we will not put your name on the project forms, but we will write down your trailer’s 

address or a unique identification number assigned by the CDC. 

You can change your mind and decide that you do not want us to test your trailer. If you 

do change your mind, it will not affect any of your benefits from the Federal 

Government. 

____________________________________ _________ _________

Adult resident’s Name Date Time

____________________________________ _________ _________

Person Obtaining Assent Date Time

“In my opinion, this person cannot give informed assent.”

____________________________________ _________ _________

Person conducting telephone interview Date Time
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 42

APPENDIX D:

INFORMED CONSENT FOR PARTICIPATION

Evaluation of Formaldehyde in Occupied FEMA Owned Temporary Housing Units

For all potential participants, the informed consent document will be available for the 

participant to read or, if requested by the participant, will be read out loud. Participants 

will be required to provide a signature to document informed consent. The informed 

consent document will request permission for collection and testing of a laboratory 

sample.

(Flesch-Kincaid Reading Level for English text below = 5.2)

1. Introduction and purpose

We are working for the Centers for Disease Control and Prevention (CDC). CDC 

is working with the Federal Emergency Management Agency (FEMA) to find out 

whether there is formaldehyde (a potentially harmful chemical) in the trailers 

people are living in. We have picked some trailers at random, like flipping a coin. 

We are asking the people who live in those trailers to let us test their inside air for 

formaldehyde. We have picked your trailer as one that we would like to test.

What we learn will help CDC and FEMA make decisions on housing placement 

priorities and if some people need to be moved into different trailers to protect 

their health. The testing process will include air testing which will take no more 

than one hour and a half. At the same time there will be a brief inspection of the 

trailer for up to 30 minutes, and some questions to be answered by you for up to 

15 minutes. Section 301 of the Public Health Act permits us to collect such 

information. No cooking or smoking will be allowed during the testing process. 

We are doing this testing in a scientifically valid way. That means that we choose 

the trailers to test instead of letting people ask to have their trailer tested. You 

and FEMA will learn the formaldehyde level in your trailer, and FEMA will learn 

the formaldehyde levels across many other trailers. This will help FEMA make 

decisions to protect people’s health. 

You can choose to be part of this project or not. We will explain what we want to 

do to you so you can decide. Please ask us questions if you do not understand 

something. If you choose to be part of this project, you will need to sign this 

form. Then we will give you a copy of this form. 

2. Freedom of choice

If you agree to be in this evaluation, you can learn more about your home 

environment. If the formaldehyde level in your trailer is high, you may be given 

priority for housing relocation.

3. Benefits/Risks
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 43

Everything you tell us and all your test results will be kept private to the extent 

allowed by the law. To protect your privacy, we will not put your name on the 

project forms, but we will write down your trailer’s address or a unique 

identification number assigned by the CDC. We will tell FEMA about the levels 

of formaldehyde in each trailer. Personally identifying data will be destroyed by 

the CDC, but left at the Louisiana and Mississippi Departments of Public Health 

at the completion of the study. 

4. Confidentiality

It will not cost you anything to have your trailer tested as part of this project. You 

will be compensated for your time and inconvenience with a $50 gift card at the 

completion of the study.

5. Cost/Payment

Before we start, we want to make sure you understand that it is up to you whether 

or not to join this project. You have the right to ask us to stop the testing at any 

time for any reason. 

6. Right to refuse or withdraw

If you have any questions please feel free to ask us now.

7. Persons to contact

If you have questions later, please contact:

Matt Murphy at 770-488-3417 or 

Gary Noonan at 770-488-3449 

If you feel that you have been harmed by this evaluation or if you have any 

concerns about your rights, please contact the CDC Deputy Associate Director for 

Science in Atlanta, Georgia, USA at 800-584-8814.

I agree to allow the air in my trailer to be tested. The information in this informed 

consent form has been explained to me. I have been given a chance to ask 

questions. I feel that all of my questions have been answered. I know that it is 

my choice to allow the air testing or not. I know that if I agree to the testing I can 

have it stopped at any time. 

8. Your consent

I give permission for an air sample to be collected and 

tested for formaldehyde, and for the temperature and 

humidity to be measured in my home.

□ YES □ NO

I have read or had this form read to me. By signing below, I consent to the air testing and 

to providing answers to the survey questions.

_____________________________________________ ______________________

Name and signature of participant Date (mm/dd/yyyy)
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 44

_____________________________________________ ______________________

Name and signature of witness Date (mm/dd/yyyy)

Office use only

Place ID label here
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 45

APPENDIX E:

EXPOSURE ASSESSMENT QUESTIONNAIRE AND WALK THROUGH 

SURVEY

INTERVIEWER SCRIPT:

The purpose of this part of the interview is to collect some information about you and 

your FEMA trailer environment. If there is a question that you do not want to 

answer, please let me know and we can skip it. All of your responses will be kept 

private and will not affect any of the home or health care services that you currently 

receive.

This interview will begin with a few questions about your age and where you work. 

We will then look at the inside and outside of your trailer. We will walk around and 

through your trailer with you to make some observations. 

Office use only

Place ID label 

here
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 46

 

 Form Approved 

 

OMB No. 0920-0008

 

Expiration Date 3/31/2010 

EXPOSURE ASSESSMENT QUESTIONNAIRE AND 

WALK THROUGH SURVEY

Date ___________________ (mm/dd/yyyy)

Interviewer initials ___________________

Trailer VIN ________________________ Trailer barcode _________________

Trailer type:  Travel trailer  Mobile home  Park  Other 

Street address: 

____________________________________________________________

County: _______________________ State (circle one): LA / MS

Zip code: _______________________

Is this home located on private land or in a federal/commercially owned park?

 Private land  Park 

If a park, please indicate the park name: _______________________________________

Trailer occupied since _______________________ (mm/dd/yyyy)

Who pays for your utilities?  Self  FEMA  Other 

Total number of residents in trailer _______________

Number of residents in trailer, by age group _______________ adults (≥18 years)

 ________________children (≥13-<18 yrs)

________________children (3-<13 yrs)

________________children (<3 yrs)

May we contact you if we have any additional questions?  Yes  No

If YES, what is the best phone number to use and time of day to call?

Phone: ( ) ___________________ Time: _____________ AM / PM

Alternate: ( ) ___________________ Time: _____________ AM / PM

 Public reporting burden of this collection of information is estimated to average 10 minutes per response, 

including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data 

needed, and completing and reviewing the collection of information. An agency may not conduct or sponsor, and a

person is not required to respond to a collection of information unless it displays a currently valid OMB control 

number. Send comments regarding this burden estimate or any other aspect of this collection of information, including 

Office use only

Place ID label 

here
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 47

suggestions for reducing this burden to CDC/ATSDR Reports Clearance Officer; 1600 Clifton Road NE, MS D-74,

Atlanta, Georgia 30333; ATTN: PRA (0920-0008)
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 48

Pests 

1. Have pesticides been sprayed inside 

your home the past month?

 Yes

 No

 Don’t know

Indoor environment 

2. Does your trailer have air 

conditioning? 

 Yes

 No (go to question # 4)

3. During the past 2 weeks, how many 

hours—on average—did you keep 

your air conditioning running every 

day? 

 Less than 1 hour 

 1–4 hours 

 5–8 hours 

 More than 8 hours 

 Don’t know

4. During the past 2 weeks, how many 

hours—on average—did you keep 

your heater running every day? 

 Less than 1 hour 

 1–4 hours 

 5–8 hours 

 More than 8 hours 

 Don’t know

 No working heater in trailer

5. Do you regularly use space heaters?  Yes

 No 

 Don’t know

6. Were the windows, scuttles, and/or 

door open in the past 3 hours?

 Yes

 No (go to question # 8) 

 Don’t know

7. Approximately how long did you 

keep your windows and/or door 

open before this visit?

 Less than 1 hour 

 1–4 hours 

 5–8 hours 

 More than 8 hours 

 Don’t know

8. Did anyone smoke in here in the 

past 3 hours?

 Yes

 No 

 Don’t know

9. During the past two weeks, how 

many people have smoked in here? # People: _____________

10. How many packs of cigarettes are 

smoked in this house each day?

 None

 < 1⁄2 pack

 1⁄2 - 1 pack 

 >1 – 2 packs 

 > 2 packs

 Don’t know

11. Does anyone cook in here?  Yes

 No (go to question #13)

INTERVIEWER QUESTIONNAIRE

Office use only

Place ID label 

here

Office use only

Place ID label 

here
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 49

 Don’t know

12. Did anyone cook in here the past 3 

hours?

 Yes

 No 

 Don’t know

Daily activities

13. What is the average amount of time 

that you spend inside your trailer 

each day?

 Less than one hour 

 1-4 hours 

 5-8 hours 

 More than 8 hours 

 Don’t know

14. Do you or your household 

members sleep in this trailer?

 Yes

 No 

 Don’t know

15. Were any of the following used 

here in the past week? 

 Candles

 Air fresheners

 Glue, paint, furniture finish

 Mothballs

 Closet fresh (mildewcide)

 Nail polish

16. Do you have any pets that you keep 

in here and how many? 

 Dog #:_____

 Cat #:_____

 Bird #:_____

 Other:___________ #:____

17. Have you noticed the roof leaking 

in the past 3 months?

  Yes

  No 

 Don’t know

18. Have you noticed pipes leaking in 

the past 3 months?

  Yes

  No 

 Don’t know

 19. Have you noticed mold in your 

home during the past 3 months?

  Yes

  No 

 Don’t know
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 50

Questions pertaining to the trailer (Check all that apply)

1. Do you see any problems with the 

roof (for example sagging or 

holes)?

 Yes 

 No

 Unable to see entire roof

2. Are there signs that water spills 

onto siding?

 Yes

 No

3. Are there any signs of mold in the 

living area of the trailer?

 Yes

 No

 If YES, estimate size of mold 

 growth?

  < 1 sq. foot

  1-4 sq. feet

  > 4 sq. feet

4. Is there carpeting in the trailer?  Yes

 No

 5. What type of air conditioning does 

the trailer have? 

 Central AC/forced air

 AC/chiller on roof of 

 Trailer

  No working AC system

 Other:_________________ 

6. What type of heating does the trailer 

have?

 Central heating/forced air

  Space heaters

  No working heating system

 Other: _________________ 

7. What type fuels are used for 

cooking?

 Electricity

 Propane Gas

 Natural Gas

 Charcoal or wood 

 Other: _____ 

8. Is there a functioning smoke 

detector?

 Yes

 No

Notes: __________________________________________________________________

________________________________________________________________________

INTERVIEWER WALK-THRU OBSERVATION Office use only

Place ID label 

here
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 51

APPENDIX F:

ENVIRONMENTAL SAMPLING PROTOCOL

Formaldehyde Samples

Analysis Method:

Formaldehyde samples will be collected using the NIOSH Manual of Analytical Methods 

(NMAM) Method 2016 with Supelco S10 LpDNPH cartridges. The limit of detection 

(LOD) shall be 0.07 microgram per sample and the limit of quantification (LOQ) shall be 

0.23 microgram. Lower LOD and LOQ are acceptable. A minimum quantifiable 

concentration of 0.0063 parts per million is required with a 30 liter sample volume 

collected over one hour. The definition from the NMAM should be used for LOD and 

LOQ (http://www.cdc.gov/niosh/nmam/pdfs/glossary.pdf).

Sample Collection:

Samples will be collected at a flow rate of 500 ± 50 milliliters per minute for one hour. 

Each sample will be collected in the center of the trailer primary living room on a four 

foot tall stand that mimics the breathing zone height of an adult when sitting. Residents 

will be asked to configure doors and windows as they would have them while they slept. 

Sampling will be under observation by one of the sampling team members at all times. 

Every tenth sample collected by a team will be a duplicate sample. Sampling will occur 

during a specific window of time per day for all trailers which is between 10:00 AM –

8:00 PM. No cooking or smoking in the trailer will be allowed during the one-hour 

sample collection period. 

Quality Assurance and Control:

Six to ten, or additional as required by the lab, media blanks will be taken from each lot 

of sample tubes. The media blanks should be taken from the start of a lot (2 to 3), from 

the middle of a lot (2 to 4) and from the end of a lot (2 to 3). All media blanks should be 

logged on the chain of custody sheet and sent for analysis on the day that they were 

collected with the field blanks and samples.

Two to ten, or additional as required by the lab, field blanks will be collected on each day 

in which samples are collected. This can be divided by travel groups, (groups consisting 

of teams that are operating in close proximity or who are traveling together). All field 

blanks should be logged on the chain of custody sheet and sent for analysis on the day 

that they were collected with the media blanks and samples.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 52

Sample Handling:

Sample tubes will be stored in a freezer or in a cooler on ice at all times (upon receipt, 

while not being used for sampling, and during shipment to the laboratory).

At the end of each sampling day samples will be shipped to the analytical laboratory 

either overnight or if collected after the last overnight drop off time the next morning in 

coolers with chain of custody documents enclosed or attached. Samples collected on 

Saturday and Sunday will be stored on ice or in a freezer and shipped by overnight means 

with the appropriate chain of custody documents to the analytical laboratory on the 

following Monday morning.

Temperature and Relative Humidity

Temperature and relative humidity will be logged using a HOBO® brand temperature 

and relative humidity logging instrument manufactured by Onset Computer Corporation 

(or equivalent) and will be set to collect data at five minute intervals. Data will be 

collected during the site visits for a minimum of 5 minutes before and 5 minutes after the 

collection of the formaldehyde sample at each trailer. Data logs will be divided into 

individual logs for each sample. A suggested method for this is to flag the start and stop 

times by an event marker at the start and finish of data collection. Data will be 

downloaded to a laptop at end of each day. Files will be labeled with site #, date, and 

visit number in a standard form. Data event flags will be confirmed on the sample 

collection data sheet. Files will be e-mailed each day to the database manager.

Data Sheets

Data sheets will be filled out prior to and during site visit. Information about trailer

received prior to site visit will be confirmed at time of site visit. Data sheets will be 

faxed or sent overnight each day to the database manager.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 53

SAMPLING STANDARD OPERATING PROCEDURE

Preparation prior to site visit:

Formaldehyde

Operational Checks:

1) Pump and calibrator batteries checked for charge and functionality.

2) Pump flow rates calibrated to 500 ± 50 milliliters per minute.

3) Sample tubes lot # and expiration date checked. 

(Expired tubes will be discarded)

4) If necessary, collect media blanks and label.

5) Stock coolers with “Blue Ice”

6) Sample tubes placed in cooler in number to be equal to trip blanks and samples to be 

collected + 2.

Temperature and Relative Humidity 

Turn on HOBO® instrument and check for proper operation.

Operational checks:

1) Confirmation of time synchronization 

a) Time must agree ± 1 minute with Formaldehyde Chronometer.

b) Time should be adjusted if necessary.

2) Confirm readings of HOBO® meet manufacturer’s specifications.

a) Temperature readings must be ± 0.63o C of average temperature reading of all 

HOBO® instruments in group.

b) Humidity readings must be ± 2.5% of average humidity reading of all HOBO® 

instruments in group. 

c) Any HOBO® falling outside the manufacturer’s specifications will be flagged as 

out of calibration and removed from service until a calibration is performed.

3) Confirm that HOBO® is set to log Temperature and Humidity measurements at five 

minute intervals.

a) Adjust to 5 minute data logging interval if necessary.

b) Confirm event marker is operating correctly. (If not remove from service)

Data Sheet

10. Confirm information is correct for scheduled site visits.

11. Confirm sheets for all scheduled site visits are present.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 54

Site Visit:

 

Formaldehyde

1. Calibrate pumps to a flow rate of 500 ± 50 milliliters per minute. 

2. Record pump identification and pre-sample flow rate data on data sheet.

3. Label Sample tube.

4. Sample tube and trip blank data recorded on data sheet.

5. Sample tube set on tripod at central unobstructed location in the THU at breathing 

level.

6. Pump started and time recorded on data sheet.

7. Sample collected for 60 ± 2 minutes. 

8. Pump stopped sample immediately capped and stop time recorded on data sheet.

9. Sample returned to cooler.

10. Pump post sample flow rate checked and recorded on data sheet.

11. Sample identification on tube confirmed with data on sample sheet.

12. Trip blanks will be recorded, processed, labeled and returned to cooler.

Temperature and Relative Humidity

1. Confirm that data logger is operating. 

a. LED blinks. 

2. Activate event marker at least 5 minutes prior to start of formaldehyde sample.

a. Press button for one second.

3. Record start time for HOBO® sample on data sheet.

4. Continue sampling until at least 5 minutes after completion of Formaldehyde 

sample, activate event marker to indicate end time of data collection. 

a. Press button for one second

5. Record stop time on data sheet.

Data Sheet

1. Confirm with the occupants that information previously provided is correct 

2. Completely fill out data sheet.

3. Have second team member confirm that data sheet is complete.
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 55

Post Site Visit:

Formaldehyde

Monday - Friday samples

1. Confirm that the proper numbers of field and media blanks are enclosed.

2. Chain of custody documents completed for each sample. 

3. Cooler “Blue Ice” refreshed.

4. Cooler sealed and shipping label affixed for overnight shipment to lab. 

Saturday and Sunday samples

1. Confirm that the proper numbers of field and media blanks are enclosed. 

2. Chain of custody documents completed for each sample.

3. Samples stored in freezer.

Monday morning

1. Cooler “Blue Ice” refreshed.

2. Cooler sealed and shipping label affixed for overnight shipment to lab. 

Temperature and Relative Humidity

1. Data downloaded to a laptop hard drive. 

a. Data files will be named with Site #, date and visit number in the form – LA 

001.10-12-2007.01. (Or similar)

2. Data file event marks will be checked against data sheet start and stop times. 

3. Data e-mailed to data base manager. 

Data sheet

Fax or overnight data sheet to data base manager. 
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 56

APPENDIX G:

SAMPLE DATA SHEET FOR FORMALDEHYDE, TEMPERATURE, AND 

RELATIVE HUMIDITY DATA COLLECTION

Date ___________________ (mm/dd/yyyy)

Sampling Team ______________________

TRAILER INFORMATION 

THU Manufacturer ________________________________________________ 

THU Model ________________________________________________

VIN Number ________________________________________________ 

Unique Trailer ID ________________________________________________

Date of Manufacture _______________________ (mm/dd/yyyy)

THU Address ________________________________________________

THU Type  Travel trailer  Mobile home  Park  Other 

Unit Faces: N S E W (circle one)

Neighborhood North: 

Residential/Office/Retail/Manufacturer/Other_____________ 

South: 

Residential/Office/Retail/Manufacturer/Other_____________ 

East: 

Residential/Office/Retail/Manufacturer/Other_____________ 

West: 

Residential/Office/Retail/Manufacturer/Other_____________ 

Comments:

Office use only

Place ID label here
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 57

APPENDIX G, con’t: 

SAMPLE DATA SHEET 

Date ___________________ (mm/dd/yyyy)

Sampling Team ______________________ 

TEMPERATURE and RELATIVE HUMIDITY

Sample Location ___________________________ 

Sampling Height (inches) ___________________________ 

HOBO No. ___________________________ 

HOBO S/N ____________________________ 

Start Time _____________ AM/PM Stop Time _____________ AM/PM 

HOBO Data File Name

 ___________________________________________________ 

FORMALDEHYDE SAMPLE

Sample Number _____________ Tube Lot 

 __________________ 

Pump Number S/N _____________ Tube S/N 

 __________________ 

Pre-Sample Calibration Flow (LPM) _________ Start Time _________ 

AM/PM

Post-Sample Calibration Flow (LPM) _________ Stop Time _________ 

AM/PM

Average Flow (LPM) ______________ Sample Time (min) 

_____________ 

Sample Volume (L) ______________ 

Field Blank S/N ______________ Chain of Custody 

#_____________ 

Shipped via ______________ Shipping # 

____________________ 

THU ENVIRONMENT DURING SAMPLING

Number of windows open:  0  1  2  3  4 

Door open?  Yes  No  Don’t know 

Air conditioning on?  Yes  No  Don’t know 

Heat on?  Yes  No  Don’t know 

Exhaust hatch open?  Yes  No  Don’t know 

Office use only

Place ID label here
Final CDC Findings—Formaldehyde Levels in FEMA-Supplied Trailers 58

Comments: 

Corrections: