Industrial ventilation is most necessary to remove excessive temperature. Clean, fresh, and uncontaminated air is the basic need of life. The human body can not tolerate excessive temperature. Heat stress produced by very hot or cold exposure causes adverse effects on the health and safety of work people.
The industry has many pollutants which contaminate air and heat stress is generated due to the hot processes. Well-designed and effective ventilation helps in removing excessive temperature.
Heavy physical work or heavy workload causes heat stress and strain and increases metabolic heat, body temperature sweating, heart rate, etc. To maintain body temperature ventilation is most necessary.
Basic functions of industrial ventilation:
- Maintain the oxygen content of the air and prevent CO, concentrations from rising.
- Prevent or remove body odors.
- Prevent harmful concentrations of aerosols and air-borne contaminants and.
- Maintain reasonable conditions of thermal limits for comfort and efficiency which result in decreased heat stress, increased productivity, reduced accident rates (hot conditions induce unsafe acts) and adverse health effects (interaction with other hazards), higher level of job satisfaction, reduced absenteeism, improved attitudes, reduced downtime for hot vessels and compliance of required standards.
Benefits of industrial ventilation:
- Availability of sufficient fresh air for breathing or life.
- Removing oxygen deficiency from a confined space.
- Removal or dilution of carbon dioxide and other air pollutions.
- Decrease in environmental heat or temperature.
- Increase in air changes per hour as per statutory requirement.
- Maintaining metabolic body temperature or heat balance.
- Removal of air contaminants (dust, gas, fumes, mist, etc) from the workroom.
- Maintaining room temperature for comfort
- Providing desired air conditioning (cooling or heating).
- Removal of body odor and bad smell from the room.
- After heavy physical work, evaporating body sweating and making the body cool.
- Decreasing discomfort and distress.
- Maintaining the efficiency of work.
- Decreasing chances of accidents and maintaining safety and productivity.
- Providing better job satisfaction and good attitudes.
- Increasing cooling rate of hot vessels or hot substances.
- To maintain overall comfortable working conditions and
- To help compliance with statutory provisions and standards.
The quantity and quality of air required for ventilation:
- Rates of heat generation in the room.
- Rates of contaminants (gas, vapor, dust) generation in the room.
- Rates of dispersion of heat & contaminant.
- Rates of dilution and/or removal that may be achieved by ventilation.
These parameters should be measured to assess the performance of ventilating systems:
- Capture velocity.
- Air volume flow rates in various places in the system.
- The pressure losses across filters and other fittings and pressures developed by fans.
Problems in Hot Environment:
Types of health disorders caused by exposures to high heat.
- Skin disorders.
- Systemic disorders.
- Psychoneurotic disorders
These disorders can cause the following effects
- Heat or sun stroke due to excessive rise in core (body) temperature ‘resulting from failure of thermo regulatory mechanism.
- Heat Exhaustion due to loss of body fluid (with salt) in sweating.
- Heat or muscle cramps due to profuse sweating and salt loss, drinking much water and failure to replace body’s salt loss.
- Fainting due to more blood in the skin and lower part of the body, less return to the heart for pumping to the brain.
- Heat Rush or Prickly Heat likely to occur in hot and humid environment where sweat is not easily removed from the skin surface and sweat glands plugged.
- Transient heat fatigue due to prolonged heat exposure.
Parts of an industrial ventilation system:
An industrial ventilation system has two main parts: a fresh air supply system and an exhaust system.
- Air supply system consists of air inlet,
- air filtering equipment,
- heating/cooling equipment,
- air distribution registers.
The exhaust system consists of:
- an “air intake” area,
- ducts to move air from one area to another,
- air cleaning device(s),
- fan(s) to bring in outside air and exhaust the indoor contaminated air, and
- discharge stacks.
Types of industrial ventilation systems:
There are two basic types of industrial ventilation systems.
- Dilution ventilation system.
- Local exhaust ventilation system.
Dilution ventilation system:
Dilution ventilation systems reduce the contaminant concentration on the air by mixing contaminated air with clean and fresh air. It is helpful in the control of health and fire hazards. It is not useful to control fumes dust and contaminants of high toxicity and high quantity or concentration.
But where air pollution is not very high and the toxicity level is low to moderate dilution ventilation is useful. It requires less maintenance and is best for mobile contaminant sources.
Advantages of dilution ventilation:
- It requires less maintenance.
- Installation cost is very low and it requires lower equipment.
- Dilution ventilation effective for low toxic chemicals.
- Effectively controls flammable or combustible gases or vapours.
- It is best ventilation for mobile or dispersed contaminant sources.
Dis advantages of dilution ventilation:
- It cannot remove contaminants completely.
- It is not used for highly toxic chemicals.
- It is not useful to control fumes, dusts and high toxicity contaminants.
- Large quantities of heated or cooled make up air is required.
- Not recommended for irregular emission of contaminants.
Local exhaust ventilation:
Local exhaust ventilation is applied at the release points of contaminants (Dust, gas, fumes, etc) to reduce their concentration in the workroom below TLVs. Where the emission of heat or contaminants is high local exhaust ventilation is best to use. It requires less energy than dilution ventilation.
What is emergency ventilation?
It is a type of mechanical local exhaust ventilation where specialized air ducts for delivering air may not be necessary. It is useful in gas-generating plants and compressor rooms where the risk of a sudden outburst of explosive or flammable gases or vapors exists. At least 8 air changes per hour are necessary. Axial fans are selected for spark-free operation. Automatic switches are required to operate the system at the time of emergency.
FAQ for industrial ventilation:
What is the purpose of a ventilation system?
There are four purposes of ventilation:
1. Provide a continuous supply of fresh outside air.
2. Maintain temperature and humidity at comfortable levels.
3. Reduce potential fire or explosion hazards.
4. Remove or dilute airborne contaminants.
what are the limitations of the dilution ventilation system?
1. It does not remove contaminants completely.
2. It can not be used for highly toxic chemicals.
3. It is not effective for dust or a large amount of gas or vapors.
4. It requires a large amount of makeup air to be heated or cooled.
5. It is not effective for handling surges of gases or vapors or irregular emissions.
How do I know which type of ventilation system is best for the workplace?
All industrial ventilation systems, when designed properly, should be able to provide long-term worker protection.