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Guide to the 2010 NFDA Prep Room Ventilation Report


In September 2010, the the National Funeral Directors Association (NFDA) issued a new and groundbreaking report on ventilation in the preparation room, along with practical, cost-effective recommendations for removing formaldehyde vapors during embalming. The report, "Formaldehyde Vapor Reduction in the Funeral Home Preparation Room: Recommendations for Effective Preparation Room Ventilation," is based on a year-long study of funeral homes and their ventilation systems, and an evaluation of ventilation engineering practices for the control of formaldehyde.

Download the report "Formaldehyde Vapor Reduction in the Funeral Home Preparation Room: Recommendations for Effective Preparation Room Ventilation"

A. Background

1. Rationale for the Study
2. Scope of the Study
3. Findings

B. 5-Step Guide for Effective Preparation Room Ventilation

1. Formaldehyde Ventilation Assessment
2. HVAC Consultation
3. Evaluation
4. Changes
5. Implementation and Maintenance Scheduling

C. Abbreviations, Terms, References


Formaldehyde Vapor Reduction in the Funeral Home Preparation Room: Recommendations for Effective Preparation Room Ventilation

NFDA members may download the entire report from the website free-of-charge. Hard copies are available to members free-of-charge and at a cost of $70 to nonmember; call NFDA at 800-228-6332 to order a printed copy of the study.

All documents are in PDF format and require you to log into the NFDA website. If you do not know your login ID or password, please call your personal NFDA member service representative at 800-228-6332.

Download the full report and appendixes (1.76 MB, PDF, member login required)

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A. Background

The August 2010 NFDA study, "Formaldehyde Vapor Reduction in the Funeral Home Preparation Room: Recommendations for Effective Preparation Room Ventilation," was prepared by William B. Ridenhour, PE, of Coherent Sciences, LLC, Bowie, Maryland. The study is the property of NFDA.

1. Rationale for the Ventilation Study

The ventilation study provides an important practical guide to removal of formaldehyde vapors in the preparation room. NFDA conducted the study because:

  • Ventilation is the single most effective way to control formaldehyde vapor levels in the preparation room.

  • International and domestic agencies recently have examined formaldehyde because of increasing concerns about its health effects. In 2004, the International Agency for Research in Cancer (IARC) found a link between formaldehyde and nasal cancer and in 2009, IARC found a link between formaldehyde and leukemia. The 2009 IARC finding was based, in part, on a National Cancer Institute study of funeral directors. EPA and the National Academy of Sciences continue to study formaldehyde health risk.

  • There are no consensus ventilation standards that apply to funeral home preparation rooms. This study fills that void.

  • NFDA's mission is to educate and protect funeral directors and make sure that they are informed about important issues affecting their health and safety. Whether formaldehyde is ultimately determined to cause cancer in funeral directors or not, there is no good reason for any person to be exposed to a toxic compound in the preparation room, when simple, cost effective measures can be taken to reduce that exposure.

2. Scope of the Study

The simple objective of the study was to identify those features of an effective ventilation system that would remove formaldehyde from the breathing zone of the embalmer.

The study was conducted by William Ridenhour, a leading HVAC consultant, whose experience includes designing and auditing laboratories for the federal government.

Using his HVAC experience and knowledge of formaldehyde and its properties, Ridenhour inspected funeral homes to examine their ventilation systems and conducted an extensive literature search to identify those preparation room activities that were shown to produce the most significant formaldehyde rates. This research enabled Ridenhour to assess how ventilation systems addressed formaldehyde vapors and what improvements could be made.

3. Findings

The study reached a number of conclusions of critical importance to funeral directors. Several of the key findings are summarized below:

  • Air change rate alone, that is, the number of times per hour that fresh air enters the preparation room, does not guarantee effective formaldehyde removal. The study recommends no less than 15 air changes per hour although attention needs to be given to other factors.

  • The flow of air in the preparation room is key. Sources of air supply and grilles for air removal need to be located so that airflow is controlled and formaldehyde vapors do not reach the embalmer's breathing zone.

  • A local exhaust ventilation (LEV) device should be evaluated as an addition to the ventilation system. An LEV, designed with a small hood attached to a flexible arm, located between the embalmer's breathing zone and the embalming table, can capture formaldehyde vapors at their source. LEVs have been used in many settings to remove toxic gases.

  • A ventilation system needs to reflect the funeral home's business, including whether there are two or more embalming tables in use at the same time, whether more than one embalming is performed daily, the percentage of autopsied and organ donor cases, and use of cavity fluid, osmotic gel and accessory compounds, which are considered to cause the highest formaldehyde generation rates.

  • The report concludes that an effective ventilation system, designed, operated, and maintained to meet the criteria in the study, can be effective in removing formaldehyde vapors from the breathing zone of the embalmer in the preparation room and lowering overall levels of formaldehyde. The criteria follow:

Criterion 1. The ventilation system should be a dedicated, non-recirculating system.

Criterion 2. As a general proposition, the minimum air change rate for the preparation room should be no less than 15 air changes per hour.

Criterion 3. The ventilation system should exhaust more air from the space than it supplies to the space to create a slightly negative pressure within the preparation room relative to adjacent spaces in the funeral home.

Criterion 4. The number and location of supply diffusers and exhaust grilles should be adequate to direct a sufficient amount of air across the preparation table(s) so that formaldehyde vapors are transported away from and out of the embalmer's breathing zone.

Criterion 5. Installation of an LEV device, designed to serve the preparation table(s), will control formaldehyde at its source and enhance the effective operation of a general ventilation system.

  • The design, installation, maintenance, and alteration of the preparation room ventilation system should always be in consultation with an HVAC professional to ensure the system is functioning effectively to reduce formaldehyde exposure to the greatest extent possible.

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B. 5-Step Guide for Effective Preparation Room Ventilation

An essential preliminary step for the funeral home is to assemble all information about the current preparation room ventilation system.

  • Ensure that you have a basic working understanding about your prep room ventilation system, its components, and how it operates.

  • Locate the most recent OSHA test results.

  • Maintain all ventilation system and OSHA test result information in one place.

STEP 1. Complete the Formaldehyde Ventilation Assessment

Completing the Funeral Home Preparation Room Formaldehyde Ventilation Assessment will provide your funeral home with the following:

  1. A guide to the important elements of a well-functioning ventilation system;
  2. Information about how prep room activities and choice of products influence ventilation considerations;
  3. Details about your own ventilation system;
  4. Information for an HVAC expert to evaluate or revise an existing preparation room ventilation system or to design a new ventilation system for a renovated preparation room or one that is to be constructed.

NFDA members may click here to download the Funeral Home Preparation Room Formaldehyde Ventilation Assessment. Members may also call NFDA at 800-228-6332 for a free printed copy of the report, which contains the preparation room assessment.

Nonmembers must puchase a printed copy of the study at a cost of $70 to obtain the preparation room assessment; call NFDA at 800-228-6332 to order a printed copy of the study.


STEP 2. Complete Expert HVAC Consultation

NFDA strongly recommends the periodic re-evaluation of the preparation room ventilation system by an expert HVAC consultant.

Select an experienced consultant, ideally an expert who has done prior work with prep room ventilation or hazardous substance capture and control.

Arrange for a consultant to assess your prep room ventilation system if you lack information about the system or if you have not used an HVAC expert in the last three years, in order to assure that the ventilation system continues to function effectively to remove as much formaldehyde as possible. Effective ventilation is the most important factor in the capture and control of formaldehyde vapors in the preparation room.

Ventilation is determined in relation to site-specific factors, including prep room design and configuration and the nature and size of the funeral home's business, number of tables in the preparation room, the extent to which tables are used simultaneously, and the size and configuration of the preparation room. Any ventilation system must, at a minimum, meet local code and other regulatory requirements.

  • Provide a copy of your completed Funeral Home Prep Room Formaldehyde Ventilation Assessment to the HVAC expert before the expert's visit to your funeral home.

  • As part of the HVAC consultation, ask the expert to:

a. Evaluate the effectiveness of prep room ventilation – not simply whether OSHA standards are met
b. Identify short and long actions to enhance preparation room ventilation
c. Identify improvement costs
d. Assess the utility of installing a local exhaust ventilation (LEV) device as an adjunct to the existing ventilation system.
e. Recommend needed regular maintenance for prep room ventilation

STEP 3. Evaluate Recommendations

Evaluate the expert's recommendations to determine the actions to take that will provide the greatest short term and long term benefits.



STEP 4. Make Simple Changes in Ventilation System

Simple changes in the ventilation system can often result in major improvements in ventilation, such as:

  • Resizing the exhaust fan
  • Relocating and resizing the exhaust grille so that it is adjacent to the embalming table(s) and near the floor

STEP 5. Scheduling Implementation and Maintenance

  • Establish a schedule to implement the expert's recommendations for improving ventilation system effectiveness and maintaining the funeral home's ventilation system. A maintenance plan should be regular (at least annual) and should focus on equipment with mechanical parts.
  • Ask the expert to show a funeral home employee what and how to maintain the system.
  • Consider the following to achieve peak ventilation performance:
    • Mechanical parts require regular lubricating
    • Filters need to be changed
    • Fans and other equipment should be cleaned to remove dust and dirt
    • Of course, if the funeral home's business has changed, promptly re-evaluate the effectiveness of the ventilation system.

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C. Abbreviations, Terms, References

ACH Air changes per hour
AC/HR Air changes per hour
cfm Cubic feet per minute
CFM/Ft2 Cubic feet per minute per sq. ft.
fpm Feet per minute
HVAC Heating ventilating and air conditioning systems
LEV Local Exhaust Ventilation
MSDS Material Safety Data Sheet
PEL Permissible Exposure Limit
ppm Parts per million
STEL Short-Term Exposure Limit
TWA Time Weighted Average
Water gauge



AIR CHANGE RATE: The rate at which outside air replaces indoor air in a space. Expressed in one of two ways: i) the number of changes of outside air per unit of time is called air changes per hour (ACH); ii) or the rate at which a volume of outside air enters per unit of time is called cubic feet per minute (cfm).

AIR HANDLING UNIT (AHU): For purposes of this report, includes equipment such as a blower or fan, heating and/or cooling coils, and related equipment such as controls, condensate drain pans, and air filters, but does not include ductwork, registers or grilles, or boilers and chillers.

BREATHING ZONE: Area of a room, in close proximity to an occupant's head in which occupants breathe as they stand, sit, or lie down.

CAPTURE VELOCITY: The velocity of air induced by a hood or local exhaust ventilation device to capture emitted contaminants as near to the point of generation as possible.

CHEMICAL HAZARD: Hazard from chemical hazardous materials such as acids, bases, solvents, cryogens, etc.

CFM: Cubic feet per minute. The amount of air, in cubic feet, that flows through a given space in one minute. One CFM equals approximately two liters per second (l/s).

DIFFUSERS AND GRILLES: Components of the ventilation system that distribute and return air to promote air circulation in the occupied space. As used in this report, supply air enters a space through a diffuser or vent and return air leaves a space through a grille.

DILUTION VENTILATION: One of the three types of workplace ventilation, which dilutes contaminants in the workplace air by blowing in clean air and exhausting some dirty air.

EXHAUST VENTILATION: Mechanical removal of air from a portion of a building (e.g., piece of equipment, room, or general area).

HAZARD CONTROL VENTILATION: An industrial exhaust system that captures and removes contaminants emitted from local sources before dilution into ambient workplace air can occur; includes chemical fume hoods, soldering bench hoods, extractor arms, glove boxes, and biological safety hoods or cabinets.

HVAC: Heating ventilating and air conditioning systems, used in building design and construction to control temperature, humidity odors, and air quality.

INDOOR AIR POLLUTANT: Particles and dust, fibers, mists, bioaerosols, and gases or vapors.

INDOOR AIR QUALITY (IAQ): Refers to the air quality within and around buildings and structures.

INDOOR AIR QUALITY VENTILATION: One of the three types of workplace ventilation, which is used primarily to provide fresh, heated or cooled air to buildings as part of the heating, ventilating, and air conditioning system.

INDUSTRIAL VENTILATION: The equipment or operation associated with the supply or exhaust of air by natural or mechanical means to control occupational hazards in the industrial setting.

LOCAL EXHAUST VENTILATION: One of the three types of workplace ventilation, which captures contaminant emissions at or very near the source and exhausts them outside, before dilution into the workplace ambient air can occur.

NEGATIVE PRESSURE: Condition that exists when less air is supplied to a space than is exhausted from the space, so the air pressure within that space is less than that in surrounding areas. Under this condition, if an opening exists, air will flow from surrounding areas into the negatively pressurized space.

OUTDOOR AIR SUPPLY: Air brought into a building from the outdoors (often through the ventilation system) that has not been previously circulated through the system.

OCCUPATIONAL EXPOSURE LIMIT (OEL): An exposure limit that is the lower of the permissible exposure limit or threshold limit value (see permissible exposure limit or threshold limit value)

PERMISSIBLE EXPOSURE LIMIT (PEL): An exposure limit published and enforced by the federal Occupational Health and Safety Administration (OSHA) as a legal standard. A PEL may be either a time weighted average (TWA) exposure limit (eight hour), a 15-minute short term exposure limit (STEL), or a ceiling (C), and may have a skin designation.

POSITIVE PRESSURE: Condition that exists when more air is supplied to a space than is exhausted, so the air pressure within that space is greater than that in surrounding areas. Under this condition, if an opening exists, air will flow from the positively pressurized space into surrounding areas.

PREVENTIVE MAINTENANCE: Regular and systematic inspection, cleaning, and replacement of worn parts, materials, and systems. Preventive maintenance helps to prevent parts, material, and systems failure by ensuring that parts, materials and systems are in good working order.

THRESHOLD LIMIT VALUE (TLV): Recommended guidelines for occupational exposure to airborne contaminants published by the American Conference of Governmental Industrial Hygienists (ACGIH). TLVs represent the average concentration for an eight-hour workday and a 40-hour workweek to which nearly all workers may be repeatedly exposed without adverse effect.

VAPORS: Gases formed by the evaporation of a liquid.

VOLATILE ORGANIC COMPOUNDS (VOCs): Compounds that vaporize (become a gas) at room temperature. In sufficient quantities, VOCs can cause eye, nose, and throat irritations, headaches, dizziness, visual disorders, memory impairment; some are known to cause cancer in animals; some are suspected of causing, or are known to cause, cancer in humans.


AIHA American Industrial Hygiene Association
ANSI American National Standards Institute
ASHRAE American Society of Heating Refrigerating and Air Conditioning Engineers
CDC Centers for Disease Control and Prevention
IBC International Building Code
NFPA National Fire Protection Agency
NIH National Institutes of Health
NIOSH National Institute for Occupational Safety and Health
OSHA Occupational Safety and Health Administration
UBC Uniform Building Codes

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