Ventilation for Workplaces and Public Transport to Prevent Spread of COVID-19 per D.O. 224, Series of 2021

Ventilation for Workplaces and Public Transport to Prevent Spread of COVID-19 per D.O. 224, Series of 2021

labor hr double bundleVentilation for workplaces is crucial in preventing the spread of COVID-19 virus pursuant to Department Order (D.O.) No. 224, Series of 2021.

Hence, on 3 March 2021 the Department of Labor and Employment (DOLE) issued D.O. 224, Series of 2021 containing guidelines to improve and maintain the quality of ventilation in workplaces and public transport.

The DOLE issuance is part of the continuing effort of the government to prevent and control the spread of COVID-19 virus at the workplace and cognizant of a large amount of working time indoors and in poorly ventilated spaces and in compliance and/or supplement to Republic Act No. 11058, DOLE Department Order No 198-18, and the OSHS of the Philippines, Section 11-B (5) of DTI-DOLE Joint Memorandum Circular No 20-04-A and DOH DM 2020-0429, adequate ventilation should be strictly enforced inside the workplace as a preventive measure against spread of COVID-19 virus.

D.O. 224 covers all commercial and industrial establishments, projects, sites, and all other places, where work is being undertaken indoors. It does not however, cover healthcare facilities requiring special considerations in the control of COVID-19.

The following terms are defined in D.O. 224, as follows:

  1. Air Change per Hour (ACH) refers to the air flow to a space expressed as volume per unit time divided by the volume of the space.
  2. Carbon Dioxide (CO2) refers to colorless gas formed by breakdown or burning of animal or plant matter and by the act of breath and may be commonly used as a surrogate indicator for assessing indoor air quality (IAQ) and ventilation efficiency.
  3. Contaminants refer to airborne contaminants such as dusts and other particulate matters.
  4. Cubic Feet per Minute (CFM) refers to unit of measurement for volume flow rate of air; this corresponds to a specific volume of air flowing through a channel per minute.
  5. Enclosed Spaces refer to areas that have means of entry or exit, surrounded by walls and a ceiling and are designed for continuous occupancy. It may or may not have windows that could be freely opened. These may include, but are not limited to, meeting rooms, conference halls, ballrooms, churches, etc. General ventilation refers to the flow of air into and out of a working area to dilute any contaminants by providing additional fresh or natural air. General ventilation can be provided through natural and/or mechanical means. Dilution ventilation, through natural, mechanical ventilation or both, should be considered  as the primary engineering control. Ventilation conditions can be evaluated  through measurement of Air Change per Hour (ACH) and Carbon Dioxide (CO2).
  6. Natural Ventilation refers to a supply of fresh air in a building and air is removed from an indoor space (ventilated) without any mechanical means.
  7. Mechanical Ventilation refers to the use of mechanical systems such as fans and often involves heating, ventilation and air conditioning (HVAC) systems to supply/provide fresh air and/or extract contaminated air.
  8. Heating, Ventilation and Air Conditioning (HVAC) System refers to the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality.
  9. High Efficiency Particulate Air (HEPA) filters refers to an air filtering device that has an efficiency of 99.97% filtration of particles up to 0.30 microns.
  10. Local air conditioning units refer to window type, ceiling mounted, floor mounted, split type, and the like, that cools, dehumidifies and recirculates indoor air.
  11. Local Exhaust Ventilation (LEV) refers to a mechanical system used to control air contaminants by trapping them at or near the source; a more effective way of controlling highly toxic contaminants before they reach the workers’ breathing zones. It is designed to capture an emitted contaminant at or near its source, before the contaminant has a chance to disperse into the workplace air.
  12. Minimum Efficiency Reporting Value (MERV) refers to a classification of air filtration devices based on their efficiency to filter particulates.
  13. Objectionable Air Draft refers to very high or too much air movement directed straight towards the workers.
  14. Open Air Spaces refer to areas that allow free air movement from all directions and may be covered by a roof, supported by posts, and not surrounded by walls. These may include, but are not limited to, covered courts, covered walkways, gazebos, etc.
  15. Other openings refer to other openings such as roof exhausters, roof ridge opening, louver openings or louvers, or door openings.
  16. Qualified personnel refers to company personnel that is knowledgeable and assigned by the employer to conduct the ventilation assessment; e.g. Safety Officer, Industrial Hygienist, Facilities Engineer/Manager, HVAC contractor.
  17. Ventilating fans refer to ceiling, wall, and pedestal fans.

General Ventilation Strategies and Recommendations under D.O. 224:

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For Non Air-Conditioned Spaces

  1. Maximize natural ventilation through the use of doors, windows and other openings, if possible and safe to do so.
  2. Ensure that the natural air brought into the workplace is free of contaminants. If natural ventilation is not feasible or inadequate, fans and air-conditioning system to supply fresh and extract contaminated air shall be used as mechanical ventilation.
  3. Dilution ventilation must be done through use of exhaust fans to achieve an air change rate of 6 to 12 ACH, while maximizing natural ventilation through the use of doors, windows and other openings, if possible and safe to do so.
  4. Exhaust fans should be kept continuously open as much as possible.
  5. If the use of ventilating fans is unavoidable, increase outdoor air changes by opening windows and other openings. Air flow direction or movement should be considered in the layout of work stations to avoid person to person viral spread through airborne respiratory droplets.
  6. Conduct weekly cleaning of windows, other openings, and ventilating fans, or as necessary.

Air-Conditioned Spaces

  1. For HVAC systems, outdoor air supply should conform to the recommended breathing zone ventilation rates, for the purpose of general air dilution and comfort control.
  2. Run the ventilation system for at least 30 minutes before and after spaces are occupied.
  3. In workplaces that only have local air conditioning units, dilution ventilation may be done through the use of exhaust fans, and filters MERV13 or higher, or high-efficiency particulate air (HEPA) filter rating applicable to the unit may be installed. Ensure that enough exhaust fans relative to the room volume are available to have the required breathing zone minimum ventilation rates.
  4. Where ventilation is greatly recirculated or access to outside air is not feasible, filters such as HEPA filtration air purifiers can be used to clean recirculated air, provided that the unit is adequate for the size of the room in which it is installed in. Ensure proper maintenance by following manufacturer recommendations of these devices.
  5. Keep the louvers of local air conditioning units in an upward position to prevent the air flowing from one person to another, while observing minimum health protocols.
  6. Frequently open the windows, doors, and other openings to supplement the mechanical ventilation systems to achieve dilution.
  7. Establish a cleaning and maintenance program for mechanical systems. Ensure that no molds or stagnant water will be circulated in the atmosphere. Filters must be changed when necessary. Appropriate Personal Protective Equipment must be worn by workers involved in the cleaning and maintenance.

Local Exhaust Ventilation (LEV)

  1. The LEV system shall conform to the existing local code. It shall have the basic components of hoods, ductworks, air cleaning device, fans or blowers and exhaust stack. All installed LEV shall be equipped with a proper air cleaning device to treat, filter and minimize airborne contaminants being exhausted to the atmosphere.
  2. Continuous operation of LEVs when workers are present in order to allow additional air change in the workplace. Ensure that running hoods of LEVs are properly secured when not being used during a specific operation to avoid disruption.

Restrooms and Water Closets

  1. Ensure that exhaust fans in restroom facilities are functional and operational at full capacity whenever the building is occupied.
  2. When toilets/water closets are used, close the toilet bowl seat lid before flushing, if available. This aims to minimize the release of droplets into air caused by flushing.
  3. Do not use hand blowers or jet dryers as it contributes to the dispersion of potentially contaminated air inside the restrooms.

Ventilation Concerns for Public Transport (Air, Rail, Land, and Sea)

Pursuant to the LTFRB MC 2020-061, Series of 2020, “Updated Health Protocols for PUVs”, DOH DM 2020-0429, “Guidance on Ventilation for COVID-19 Mitigation”, and the DTI-DOLE JMC 20-04-A and DTI-DOLE Advisory 20-03, Series of 2020, the following are advised:

  1. Provide natural ventilation and access to open air.
  2. Avoid using the recirculated air option for the vehicle’s ventilation during passenger transport.
  3. Ensure adequate ventilation, if possible, by opening windows by at least three (3) inches while in transit, provided that it is safe to do so.
  4. Ensure regular and proper maintenance of filters of the vehicle air-conditioning units, if applicable.
  5. For rail and road transport, impose a minimum of fifteen (15) seconds for the opening of doors for passengers’ exit and entry.
  6. Ensure that the following minimum public health standards are being followed:
  • Wear properly the approved face masks and face shields at all times.
  • Follow strictly the proper and frequent disinfection, before and after completing a route
  • Implement one-seat apart distance for passengers; do not allow passengers to sit beside each other, unless plastic barriers are installed between them; and disinfect regularly plastic barriers after each trip or as necessary.
  • Post updated COVID-19 information through IEC materials.
  • Avoid talking (answering phone calls or having conversations) while inside the public transport.
  • Prohibit eating and drinking while inside the public transport.
  • Do not allow symptomatic passengers on board.

The employer shall be responsible for maintaining an acceptable and safe indoor air quality. D.O. 224 provides for mechanics on ventilation assessment.

Qualitative Assessment

  1. The safety officer or any qualified personnel may use the attached self-assessment checklist (See Annex 1) in conducting the assessment.
  2. He/she shall ensure that the ventilation system is working or functioning during the conduct of assessment in order to determine how air enters and exits from the space. Other measures to assess could include, but not limited to, the following:
  • lingering smell;
  • stuffiness of room;
  • feeling of high humidity; or
  • smokiness of room.

3. The use of natural or mechanical ventilation or the combination thereof depends on the ventilation assessment conducted by a trained safety officer or ventilation/indoor air-quality specialist.

Quantitative Assessment

  1. For air movement, the directional airflow and objectionable air drafts shall be considered. Airflow direction should be from cleaner source to prevent contaminant transmission.
  2. Carbon Dioxide (CO2) is commonly used as a surrogate indicator for assessing indoor air quality (IAQ) and ventilation efficiency. CO2 concentration shall not exceed 1,000 ppm. To achieve this, the minimum ventilation in breathing zones as set by the Philippine Green Building Code, could be used as a guide (Annex 2). CO2 level inside an enclosed space may be determined using calibrated CO2 monitoring devices. During the CO2 monitoring, position the device strategically in locations such as those far from windows, doors and other openings. A calibrated CO2 monitor shall be used to ensure reliability of results.

Use of indoor plants and indoor gardens will convert the CO2 to O2. Annex 3 of D.O. 224 shows how to determine ACH.

  1. Quantitative ventilation measurements shall be performed internally by the trained safety officer or EHS personnel of the company, DOLE-OSHC, or by DOLE accredited WEM Service Providers.


As provided for in the DTI-DOLE JMC 20-04-A, the OSH Committee and/or safety officer of the workplace overseeing the enforcement and monitoring of the minimum public health standards for COVID-19 prevention in the workplace, shall include in its OSH program the monitoring and evaluation on the implementation of this Guidelines, at least on a monthly basis or as frequently as possible based on the assessment and recommendation of the OSH committee/safety officer.

Annex 1 of D.O. 224 or other similar checklist may be used to ensure regular monitoring of ventilation measures/strategies being implemented.

The DOLE Regional Offices shall monitor compliance with this Guidelines. Other government agencies shall likewise conduct its own monitoring based on their regulatory functions, as applicable. In case of violation or non-compliance, the applicable sanctions/penalties under pertinent laws, rules and regulations shall be imposed.

Rendering of Technical Assistance

The DOLE, DOH, DTI, DPWH, DILG, DOTr, DOT and the private sector partners shall extend technical assistance and support to employers and workers, and in all workplaces in complying with this Guidelines.

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