What are the best types of filters to use in HVAC systems to trap Needle Grass pollen?

In order to trap Needle Grass pollen efficiently, the best types of filters to use in Heating, Ventilation, and Air Conditioning (HVAC) systems would be those that have a high MERV (Minimum Efficiency Reporting Values) rating.

Generally, filters with a MERV rating of 11 to 13 are highly effective for removing pollen and other allergens such as dust mites, mold spores, pet dander, and the like from the air. These filters have a smaller pore size, which means they can capture and hold the tiny particles of Needle Grass pollen that smaller-rated filters might miss.

Amongst these, the pleated mechanical air filters are a great option. Their folded, pleated design provides a larger surface area for trapping particles and they are available in a range of MERV ratings.

Also, some manufacturers have specialty allergen filters, such as the Filtrete Allergen Defense by 3M, designed specifically to capture smaller particulates such as pollen. Always remember to change your filters regularly for the best results.

HEPA (High Efficiency Particulate Air) filters could be another good option, effectively capturing 99.97% of particles 0.3 microns and larger. They're usually rated at 17-20 MERV.

However, keep in mind that while higher MERV filters more particles, they also can lead to increased load on your HVAC system. Before upgrading to a high MERV filter, ensure your HVAC system can handle it.

Finally, you might supplement your HVAC filtration with a portable air purifier in the rooms where you spend most time, using HEPA technology to provide an additional layer of protection against allergens.

As always, confirm such changes with your HVAC provider or an air quality expert to ensure system safety and efficiency.