Centers for Disease Control

and Prevention

National Institute for Occupational 

Safety and Health

Summary

The National Institute for Occupational Safety and Health (NIOSH) 

has conducted several Health Hazard Evaluations [NIOSH 2019] in 

workplaces with reported health 

concerns associated with construction and renovation in occupied 

buildings. During these evaluations, NIOSH investigators identified issues that could affect indoor 

environmental quality (IEQ) such 

as a lack of dust control, the use of 

high emission building materials, 

and limited communication with 

occupants about hazards related 

to the work being done. After its 

evaluations, NIOSH made detailed 

recommendations to help employers reduce exposures and maintain 

acceptable IEQ. 

Maintaining Acceptable Indoor 

Environmental Quality (IEQ) During 

Construction and Renovation Projects

1. Ensuring that construction contractors understand and are aware of

the potential impact of construction

and renovation activities on building occupants

2. Anticipating construction and renovation activities that may generate

contaminants

3. Implementing controls to minimize exposures of both construction workers as well as building occupants

Case Studies

The following case studies demonstrate 

issues that NIOSH frequently encounters during IEQ investigations and provide recommendations that can improve the facility IEQ.

Case Study 1

NIOSH visited an office building undergoing a multi-year modernization 

project. The project included these 

changes: 

1. Upgrading the heating, ventilation,

and air-conditioning (HVAC) systems

Background

Activities during construction, renovation, demolition, or repair projects can release airborne dusts, gases, 

organic vapors, microbiological contaminants, and odors as well as produce high noise levels [ANSI/SMACNA 2007; EPA 2019; Kuehn 1996; Light 

2017]. In addition, outdoor air contaminants can be brought into the workplace.

When workers occupy spaces adjacent 

to these construction projects, the activities can trigger health complaints 

[Abdel Hameed et al. 2004; Ward et 

al. 2017]. Common symptoms reported by building occupants during these 

projects include headache, sinus problems, congestion, dizziness, nausea, fatigue, and irritation of the eyes, nose, 

or throat. These symptoms may result 

from exposures to known agents or a 

perceived risk from exposure to unknown agents [Kuehn 1996]. Kurth et 

al. [2017] found an association linking exposures to mold, dampness, and 

construction materials to asthma and 

asthma-like symptoms. 

Foresight and planning are necessary 

to reduce IEQ-related symptoms during building construction activities. 

Management strategies to reduce and 

control building occupant exposures 

should include the following: 
2

2. Improving the plumbing, electrical, and fire protection 

systems; and removing asbestos-containing material and 

lead-based paint

3. Structure modifications such as new stairways in six 

building wings 

Employees from the building wing undergoing renovation 

were temporarily moved to an adjacent wing. All of the adjacent wings remained occupied during renovation. Employees working in these wings reported dustiness, odors, 

eye and upper respiratory irritation, and asthma and allergy symptoms.

Using sulfur hexafluoride tracer gas to study air movement 

in the building, NIOSH investigators found that air flowed 

from the areas undergoing construction into the adjacent occupied office areas. Routes for the potentially contaminated 

airflow included areas around polyethylene-sheet barricades 

that were poorly sealed, holes in the ceiling where lights had 

been removed, holes in the wall board, and holes in the terra 

cotta blocks behind the baseboards. In addition, temporary 

seals over the hallway return air ducts had become loose, allowing potentially contaminated air to enter into the ventilation systems. Workers were also dry sweeping construction 

debris, which produced airborne dust.

NIOSH investigators recommended that the employer take 

the following measures to limit contaminated airflow into 

occupied areas [NIOSH 2007]:

1. Install and maintain construction walls and barricades 

and additional ventilation to keep the renovation and 

construction areas under negative air pressure relative to 

the occupied office area. 

2. Use vacuum cleaners equipped with high efficiency particulate air (HEPA) filters to clean up dust and debris.

3. Completely cover all HVAC supply and return air grills in 

the construction area and surrounding hallways to prevent contaminants from entering the HVAC systems. 

4. Communicate regularly with building occupants about the 

on-going construction work to minimize anxiety among 

the employees.

Case Study 2

NIOSH evaluated a school that had undergone recent renovations, including the addition of administrative space, library, 

classrooms, ventilation systems, electrical wiring, plumbing, 

and communications systems. The original brick school was 

built in the early 1960s with a crawl space, which had a dirt 

floor and a partial moisture barrier. The school was commissioned, which verified new systems were operating according 

to design before reopening. Employees were concerned about 

mold exposure in the newly renovated areas.

NIOSH investigators found that air flowed from the crawl 

space into the school because the exhaust fan in the crawl 

space did not work and was undersized for the area. The 

nearby ground sloped toward the building, which allowed 

surface water to enter into the crawl space. Relative humidity levels were higher in the crawl space than in the school 

building. Visible rust was present on all of the metal beams 

in the crawl space, indicating that the space had high moisture levels. Wipe samples taken from the new part of the 

school had lower fungal spore concentrations overall than 

those from the first floor of the renovated part. This indicated that there was much less mold contamination in the new 

part of the school. Carbon dioxide monitoring showed that 

the variable air volume control box for one classroom was 

not functioning correctly, which reduced the amount of outdoor air entering the space. School staff reported sinus problems and headaches that they thought were related to working in the school. 

NIOSH recommendations to reduce moisture incursion into 

the building included the following [NIOSH 2011]:

1. Maintain negative pressure in the crawl space with a 

properly working exhaust fan that is correctly sized for 

the volume to be controlled.

2. Add a complete moisture barrier to the crawl space.

3. Seal the floor penetrations.

4. Test and balancing the variable air volume ventilation system to ensure adequate ventilation in all occupied areas.

5. Re-grade the soil around the building to move surface 

water away from the building.

Recommendations

The following recommendations for maintaining acceptable 

IEQ during construction and renovation projects were developed based on NIOSH experiences from IEQ site visits 

and review of the scientific literature. Maintaining acceptable IEQ during construction and renovation activities requires a collective effort and input from building managers, 

the general contractor, subcontractors, engineers, and building occupants [ANSI/SMACNA 2007; ASHRAE 2009; EPA 

2019]. Other federal agencies have specific mandatory standards and rules that need to be followed to protect the workforce and building occupants. The Occupational Safety and 

Health Administration (OSHA) has specific standards that 

address asbestos and lead hazards. EPA has two specific asbestos guidelines for schools: Asbestos Hazard Emergency 

Response Act (AHERA), and building demolition and renovation Asbestos National Emission Standards for Hazardous 

Air Pollutants (NESHAP).

Input from HVAC professionals is important to assess ventilation system performance when making design changes or 
3

when making temporary modifications of the HVAC system 

during construction and renovation. Effective communication among all parties is essential, especially during rapidly 

changing circumstances, which are often a hallmark of construction and renovation activities. Several states have created guidelines for building renovations, especially schools 

[California Department of Education 2018; see ELI 2015 for 

additional state guidelines].

Implementing the recommendations below should reduce 

building occupant exposures. Protective measures should 

be considered according to the NIOSH [2015] hierarchy of 

controls, with an emphasis on controlling the hazard at the 

source if it is not possible to eliminate the hazard.

Initial Planning

The initial stage of any construction or renovation activity 

is the appropriate time to develop a site- and activity-specific plan to identify and control contaminants that may affect construction or renovation workers as well as building 

occupants.

 Identify all key personnel, such as representatives from the 

building and general contractor responsible for addressing 

construction- or renovation-related activities and airborne 

contaminant control, as well as other personnel such as 

building staff, engineers, and subcontractors. Engage these 

key personnel in the initial planning of the construction or 

renovation.

 Conduct an assessment of hazardous substances present 

in the building such as asbestos and lead.

 Develop a construction or renovation impact assessment 

with input from key personnel describing anticipated 

work activities along with their associated air contaminants, generation points, and areas potentially affected by 

the release of air contaminants.

 Develop a detailed plan and budget for the contaminant 

control methods that will be used.

Contract Bid Specifications

Bid specifications should be developed. In addition to general control measures detailed below, the bid specifications 

should include details about the control measures appropriate for the construction or renovation project being proposed. These bid specifications should be clearly written and 

include the elements below to reduce misinterpretation.

 Identify and provide details about the specific controls 

needed to reduce the release of contaminants into occupied areas during the construction or renovation project, 

including appropriate performance metrics.

 Require the general contractor to designate an IEQ manager and establish appropriate channels of communication 

with subcontractors. The IEQ manager should be trained 

on IEQ issues, such as air quality, acoustics, lighting, and 

temperature control, and have the authority to immediately correct problems. 

 Require training for construction employees on hazards 

and proper PPE usage (Figure 1). For construction training specifications, see the OSHA construction industry 

website.

 Develop emergency response procedures and specify conditions that would require an emergency response (such 

as a contaminant release into an occupied area).

Figure 1. Worker wearing PPE during mold removal.

Photo by EPA

Control Options

Strategies should be developed to address the specific tasks 

and building configurations as well as control of both indoor- and outdoor-generated contaminants. Some general 

considerations for control include the following:

 Schedule construction or renovation work during periods 

of low building occupancy and low occupancy adjacent to 

the work areas whenever possible.

 Isolate work areas from occupied areas using physical barriers, negative pressurization of the construction or renovation area relative to occupied areas, and use HEPA 

filtration to remove particulates (Figures 2 and 3). Techniques include the use of vestibules, double-doors, or air 

curtains as ways to prevent air movement through doorways. If the work area is large, a positive pressure buffer 

zone can be created between the work area and occupied 

area if there are no hazardous substances (such as asbestos) present that require negative pressure controls. 

 Use local exhaust ventilation with HEPA filtration where 

dust generation is anticipated. If local exhaust is not feasible, portable air cleaning devices could be used.
4

 Minimize the number of building penetrations [ANSI/

ASHRAE 2019].

 Modify HVAC operations as necessary during times of 

construction or renovation activities to ensure areas are 

kept isolated from occupied areas. This could include increasing the HVAC outdoor air intake filtration efficiency and temporarily relocating the intakes serving the occupied areas.

 Maintain an adequate unoccupied buffer zone around the 

work areas to allow for construction or renovation traffic. 

This could require temporarily relocating building occupants away from the immediate vicinity of the work areas.

 Post warning signs on barricades, construction zones, and 

other areas limiting access to authorized personnel only.

 Increase housekeeping activities in adjacent occupied areas during construction or renovation projects.

 To reduce the likelihood of contaminant generation, specify low-emitting materials for use in construction or renovation projects such as those listed in EPA’s Safer Choice 

Program [EPA 2019]. 

Implement Project Specifications

Effective implementation and management of the construction or renovation project is essential to maintain acceptable 

IEQ for the building occupants [ASHRAE 2009].

 Hold regularly scheduled meetings between building representatives, the general contractor, subcontractors, and 

other personnel as appropriate to ensure the acceptability of IEQ.

 Monitor construction or renovation activities carefully so 

that all work conforms to the bid document specifications.

 Monitor the pressurization of both construction or renovation and occupied areas to ensure that isolation of the 

work area is maintained.

 Monitor for airborne contaminants, such as particulates 

or volatile organic compounds, in the occupied areas to 

ensure acceptable IEQ.

Good Work Practices by Construction 

Workers

Good work practices and housekeeping that minimize contaminant release are essential for ensuring acceptable IEQ in 

employee-occupied areas during construction or renovation 

Figure 2. Covered entryway to prevent dust from leaving 

construction and renovation areas.

Photo by EPA

Figure 3. Full containment during renovation project.

Photo by EPA

 Upgrade the filtration efficiency of any HVAC systems 

serving occupied areas that must continue to be in use 

during construction or renovation activities to the highest 

level supported by the building HVAC systems. Inspect 

and replace filters as needed.

 Designate a storage location for construction materials 

and equipment to reduce the potential for contaminants 

to enter occupied areas. Do not store construction materials or equipment in HVAC mechanical rooms.

Protect HVAC Systems

Protect the HVAC system(s) serving the construction or renovation areas from damage or contamination.

 Disable and isolate the portions of the HVAC system(s) 

serving the construction or renovation areas to prevent 

damage or contamination, if possible.

 Block or seal supply and return air grilles in construction 

or renovation areas.
5

projects. Workers in the construction areas should use the 

following practices to reduce exposures.

 Use work practices and materials that result in little or no 

generation of airborne contaminants during construction 

or renovation activities, such as wet methods to suppress 

dust generation as well as paint and carpeting with low 

volatile organic compound emissions. 

 Establish routes for construction or renovation traffic to 

pass through unoccupied areas. Do not permit construction or renovation traffic to pass through occupied areas 

or common building openings.

 Use vacuums with HEPA filtration and damp mop regularly during construction or renovation activities to reduce dust generation.

 Bag all construction or renovation debris, and promptly remove debris from the work site through demolition 

chutes on the exterior of building and/or other dedicated 

perimeter wall openings.

 Locate dumpsters and salvage bins away from HVAC outdoor air intakes and exterior doors and windows to occupied areas.

Maintain Effective Communication

Ensure that the project manager, general contractor, subcontractors, and other personnel effectively communicate 

among themselves and with building occupants throughout 

construction or renovation.

 Before the start of construction or renovation activities, 

communicate to building occupants the scope of work 

and the precautions that will be used to control the release 

of contaminants.

 During the construction or renovation project, periodically update building occupants regarding the project’s 

progress and other pertinent information.

 Promptly respond to complaints from building occupants 

regarding construction- or renovation-related IEQ issues 

and identify any situations that would require emergency response.

 Instruct building occupants to inform their supervisor 

and seek medical care if they develop health symptoms 

that they think are related to construction- or renovationrelated IEQ issues.

Commission Work Areas after 

Completion of Construction or 

Renovation

 If possible, use 100% outdoor air to ventilate the work areas prior to occupancy to ensure acceptable air quality.

 Ensure the HVAC system(s) in the work areas are tested 

and balanced before re-occupancy.

 Monitor for airborne contaminants, such as particulates 

or volatile organic compounds, in the work areas to ensure acceptable IEQ when re-occupied.

Acknowledgments

This document was prepared by Nancy Clark Burton, Division of Field Studies and Engineering, and Susan Afanuh, 

Division of Science Integration, National Institute for Occupational Safety and Health. Kenneth Wallingford, formerly 

with NIOSH, contributed to the document.

Suggested Citation

NIOSH [2019]. Maintaining indoor environmental quality 

(IEQ) during construction and renovation projects. By Burton N, Afanuh S. Cincinnati, OH: U.S. Department of Health 

and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and 

Health, DHHS (NIOSH) Publication No. 2020‒110, https://

doi.org/10.26616/NIOSHPUB2020110

References

Abdel Hameed AA, Yasser IH, Khoder IM [2004]. Indoor air 

quality during renovation actions: a case study. J Environ 

Monit 6(9):740–744. doi: 10.1039/b402995j 

ANSI/SMACNA [2007]. IAQ guidelines for occupied buildings under construction. 2nd edition. Chantilly, VA: American National Standards Institute/Sheet Metal and Air Conditioning Contractors’ National Association, Inc. ANSI/

SMACNA 008–2008.

ANSI/ASHRAE [2019]. Ventilation for acceptable indoor air 

quality. American National Standards Institute/ASHRAE 

standard 62.1–2019. Atlanta, GA: ASHRAE.

ASHRAE [2009]. Indoor air quality guide: best practices for 

design, construction and commissioning, Atlanta, GA: 

ASHRAE. https://www.ashrae.org/technical-resources/

bookstore/indoor-air-quality-guide

California Department of Education [2018]. Indoor air quality, a guide for educators, Sacramento, CA: California Department of Education. https://www.cde.ca.gov/ls/fa/sf/

iaq.asp

ELI [2015]. IAQ during school renovations, overview of state 

laws, AZ, CO, CT, IN, MA, MS, NJ, NY, RI, VT. Washington, DC: Environmental Law Institute. https://www.eli.

org/sites/default/files/docs/iaq_renovations_final_draft_

rev_sept_2016_link.pdf

EPA [2019]. Indoor air quality (IAQ). Washington, DC: U.S. 

Environmental Protection Agency. https://www.epa.gov/

indoor-air-quality-iaq
6

EPA [2019]. Safer Choice Program. Washington, DC: U.S. 

Environmental Protection Agency. https://www.epa.gov/

saferchoice

Kuehn T [1996]. Construction/renovation influence on indoor air quality. ASHRAE J 38(10):22–29. 

Kurth L, Virji MA, Storey E, Framberg S, Kallio C, Fink J, 

Laney AS [2017] Current asthma and asthma-like symptoms among workers at a Veterans Administration Medical Center. Int J Hyg Environ Health 220(8):1325–1332. 

https://dx.doi.org/10.1016%2Fj.ijheh.2017.09.001

Light E [2017]. Maintaining IAQ while updating occupied 

schools. ASHRAE Journal 59(5):36–44.

NIOSH [2007]. Indoor environmental quality issues in a federal building. Washington, DC. By Esswein E. Cincinnati, 

OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute 

for Occupational Safety and Health, HETA 2006–0308.

NIOSH [2011]. Evaluation of health concerns in a public 

middle school — Virginia. By Page E, Burton N, Kawamoto M, Niemeier RT. Cincinnati, OH: U.S. Department 

of Health and Human Services, Centers for Disease Control 

and Prevention, National Institute for Occupational Safety and Health, NIOSH HETA No. 2010‒0045‒3129. https://

www.cdc.gov/niosh/hhe/reports/pdfs/2010-0045-3129.pdf

NIOSH [2015b]. Hierarchy of controls. Cincinnati, OH: U.S. 

Department of Health and Human Services, Centers for 

Disease Control and Prevention, National Institute for Occupational Safety and Health. https://www.cdc.gov/niosh/

topics/hierarchy/default.html 

NIOSH [2019]. NIOSH Health Hazard Evaluations (HHEs). 

Cincinnati, OH: U.S. Department of Health and Human 

Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. https://

www.cdc.gov/niosh/hhe/default.html

OSHA [n.d.] Construction industry: training and outreach 

materials. Washington, DC: U.S. Department of Labor, 

Occupational Safety and Health Administration. https://

www.osha.gov/doc/training.html

Ward AE, Azhar S, Khalfan M [2017]. Construction in occupied spaces. Slovak J Civil Engineering 25(2):15–23. 

https://doi.org/10.1515/sjce-2017-0008

For More Information

For more information about indoor environmental quality and preventing exposure during construction, visit https://www.cdc.gov/niosh/topics/indoorenv/constructionieq.html.

For more information about the NIOSH Health Hazard 

Evaluation Program, visit cdc.gov/niosh/hhe/default.html

Find NIOSH products and get answers to workplace safety 

and health questions:

1-800-CDC-INFO (1-800-232-4636) 

TTY: 1-888-232-6348

CDC/NIOSH INFO: cdc.gov/info | cdc.gov/niosh

Monthly NIOSH eNews: cdc.gov/niosh/enews/

Mention of any company or product does not constitute 

endorsement by NIOSH. In addition, citations to websites 

external to NIOSH do not constitute NIOSH endorsement of the sponsoring organizations or their programs or 

products. Furthermore, NIOSH is not responsible for the 

content of these websites.

This document is in the public domain and may be 

freely copied or reprinted. NIOSH encourages all 

readers of the Workplace Solutions to make them 

available to all interested employers and workers.

As part of the Centers for Disease Control and Prevention, NIOSH is the Federal agency responsible for conducting research and making recommendations to prevent work-related illnesses and injuries. All Workplace 

Solutions are based on research studies that show how 

worker exposures to hazardous agents or activities can be 

significantly reduced.

DOI: https://doi.org/10.26616/NIOSHPUB2020110

DHHS (NIOSH) Publication No. 2020-110

January 2020