Ventilation and Household Smoke Pollution and Its Effect to The Residents

VENTILATION

It is the intentional introduction of air into a space for diluting and displacing the pollutants- to make the air breathable. Ventilation is mainly used to control indoor air quality by diluting and displacing indoor pollutants. It can be also used for purposes of thermal comfort or dehumidification when the introduction of outside air will help to achieve desired indoor psychometric conditions. The intentional introduction of outside air can be categorized as either mechanical ventilation or natural ventilation.

Often indoor air can be more harmful than outdoor air. In 2012 the WHO reported 7 million premature death resulting from air pollution exposure (4.3 million Deaths primarily due to indoor pollution resulting from the use of wood, coal and biomass stove).

Indoor Air Quality is assured by the interaction of ventilation system with the building, and helps in dilution of contaminants to concentrations that are deemed to be acceptable for human beings and that can minimize adverse health effects.

ASHRAE

The American Society of Heating, Refrigerating and Air- Conditioning Engineers that was founded in 1894 is considered to be the pioneer in the field of setting up the required ventilation standards that provide acceptable quality air to human occupants. It publishes a well-recognized series of standards and guidelines, though not legally enforceable, except in some cases, these are generally accepted standards and are in general reviewed and revised every three years.

VENTILATION STANDARDS

Table 1: Ventilation Standard

PRIMARY REQUIREMENTS

Table 2: Ventilation Requirement

There are three main primary sets of requirements standard and a host of secondary ones. The three primary sets involve whole-house ventilation, local exhaust, and source control as shown in the above table. Whole-house ventilation is intended to dilute that the un-avoidable contaminant emissions from people, materials and background processes. Local exhaust is very intended to remove contaminants from those specific rooms (e.g. kitchens) in which sources are expected to be produced by design. Other source are control measures include to deal with those sources that can reasonably be identified and dealt with.

MINIMUM WHOLE HOUSE VENTILATION RATE

It is the ventilation rate which is assumed to be a minimum requirement for ensuring good indoor quality air considering an average low rise residential home.

From 1989 the whole-house rate in 62-2001 is set at 0.35 air changes per hour, but not less than 15 cm/person (7.5 l/s/person). The default number of people was assumed to be two for the first bedroom plus one for every additional bedroom. (Sherman

As evident from the above figure, as the number of bedroom increases, the required ventilation rate increases owing to the increase in number of people assumed to inhabiting the home. However, as the floor area increases, for same amount of pollutants mean less concentration which can be less harmful. So, as the floor area decreases, the required ventilation rate do not increases but decreases.

This rate can also be achieved two methods as below:

1. Natural Ventilation

4% of floor area as openings is considered standard; however the openings must not pose any hazards to human occupants in the living space.

2. Mechanical Ventilation

The mechanical ventilation can be achieved by using a Central Ventilation System whose flow rate is calculated using the formula described below. Such system is similar to the central Air Conditioning system with ducts running through the false ceiling and walls.

Based on formula:

Q_fan = 0.01*A _floor + 7.5(N_b + 1)

Q_fan is fan flow rate

A _floor is floor area

N_b is number of bedrooms

LOCAL EXHAUST

Contaminants are produced locally need to be dealt with locally because they can led to air pollution in other parts of the buildings if allowed to escape from place of generation. Such pollutants vary from place of generation and are generally related to the following specific parts of a building. Houses are designed to have certain activities in certain rooms. Kitchens, bathrooms, lavatories, laundries, utility rooms and toilets are all built to accommodate specific functions.

1. Kitchen
2. Bathroom

• Toilets

Such contaminants are diluted and displaced locally by

• Operable Window
• Exhaust fan

TREND IN STANDARD

• Early development in US focused on control of airborne disease like Tuberculosis
• In early 1900s, the suggested rate was 30cfm/person, and in 1925 it was set in law in 22 states
• In 1973 the recommended rate was 20cfm/person
• In 1981 it was 5cfm/person
• In 1989 it was revised to 15cfm/person
• In 1997 Standard 62.1 and Standard 62.2 were separated
• In 1999 Standard 62.2 suggested 7.5cfm/person + 0.01cfm/square foot floor area

DOWNSIDES

• Only minimum requirement, so rates must be site specific
• High-polluting events such as painting, cleaning, smoking or construction projects are not covered
• Use of unvented combustion space not covered
• One person per bedroom, with two people in the master bedroom. Higher numbers of occupants will increase ventilation needs.
• Occupants with health issues such as asthma and allergies are not covered in the standard

CONCLUSION

• Minimum requirement for having breathable indoor air
• Generally followed but not enforceable
• Room for improvement in Nepal
• More Research required

Household smoke pollution and its effect to the residents

About the 3 billion people are still cooked and heat their houses by using solid fuels (i.e. wood, crop wastes, charcoal, coal and dung) in open fires and leaky stoves. Most of them are poor and live in low and middle income countries.

Such an inefficient cooking energy and technologies produce the high levels of household smoke pollution with a range of health damaging pollutants including small soot particles that penetration deep into the lungs. In poorly ventilated system indoor smoke can be 100 times higher than acceptable levels for fine particles. Exposure is particularly high among in women and young children who spend the most of time near the domestic region.

Impacts on health

About 4.3 million People are yearly die from illness attributable to the household smoke pollution caused by the in efficient use of solid fuels (2012 data) for cooking. Among these death are

• 12% are from pneumonia
• 34% from stroke heart
• 26% from the ischaemic heart disease
• 22% from the chronic obstructive pulmonary disease (COPD)
• 6% from the lung cancer

References:
1. Mackenzie L. Davis & David A. Cornwell, “Introduction to Environmental Engineering”, McGraw Hill.
2. Gilbert M. Masters, Standford University, “Introduction to Environmental Engineering and Science”, Printice Hall.
3. Stephan Konz, Kansas State University, “Work design”, Grid Publishing Inc., Colombus, Ohio
3. C. S. Rao, “Environmental Pollution Control Engineering”, New age International (P) Limited, Publishers, India.